# simriscparams(7)

## simrisc configuration file organization
(simrisc.16.06.00)

## 2020-2026

## NAME

simriscparams - The description of the
``
configuration files

## DESCRIPTION

This page describes the organization of the simrisc configuration files. These files are formatted like standard unix configuration files. Lines are interpreted after removing initial white-space (blanks and tabs) and after removing all characters from lines starting at the first `#` character: this is considered comment and is ignored. If a line (not containing a `#` character) ends in a backslash (`\`), then the next line (initial white-space removed) is appended to the current line.

Note that all parameter identifiers are interpreted case sensitively. E.g., `Costs:` is a different parameter than `costs:`. The numeric values used in this man-page are for illustration purposes only. Some restrictions apply though: standard deviations cannot be negative; proportions and probabilities must lie in the range 0..1; multiple probabilities (like the ones used for breast densities) must add up to 1; etc. If restrictions apply then they are mentioned at the various parameter descriptions below.

## DEFAULT CONFIGURATION FILE

The configuration file provided in the simrisc distribution is
`/usr/share/doc/simrisc/simrisc.gz`.

Usually this file is unzipped by the user to the user's `~/.config` directory:

        gunzip < /usr/share/doc/simrisc/simrisc.gz > ~/.config/

whereafter `~/.config/simrisc` can be edited to contain local modifications.

Various parameters specify probability distributions. Usually the `Normal` distribution is specified. The program also recognizes the `LogNormal` and `Uniform` distributions, and uses the `Beta` distribution when handling parameter variations of the beta parameter used for lung cancer simulations (note that the similarity of the names `beta` (the parameter) and `Beta` (the distribution) is sheer accidentally).

Parameter specifications start with keywords, followed by a colon. All keywords are covered below. The format of the specifications is fixed, but empty lines and white space may be used to improve the specifications' readabilities.

Parameter specifications starting with uppercase letters (like `Scenario:`) specify (sub)sections and contain no additional specifications. Specifications starting with lowercase letters (like `ageGroup:`) are followed by actual parameter values.

The configuration file must define all parameters of all configuration sections, but configuration parameters can be modified using a separate analysis file or they can be modified by command-line parameters.

Several section namess are optional, e.g., ``Scenario:`'. In this manual page the label ``(opt.)`' is appended to the names of those sections. In actual confiuration specifications they can stil be used, but they can also completely be omitted.

## Section `Scenario:' (opt.)

This section may start with a line containing `Scenario:` and specifies some general parameters of the simulation process. The default configuration file contains the following specifications:

- `spread: false`
  when specified as `true` parameter spreading is used;

- `iterations: 1`
  the (positive) number of iterations used in a simulation loop;

- `generator: fixed`
  in addition to `fixed` the modes `random` and `increasing` are available.
  This parameter specificies the way `simrisc's` random number generators are initialized. When mode `fixed` is used the random number generators are initialized with `seed's` value; mode `random` results in the random number generators being initialized by randomly selected seeds and `seed` (below) is not used; mode `increasing` results in incrementing the seeds of the random number generators by a fixed increment at each iteration;

- `seed: 1`
  the (positive) value to seed the random number generator with. This parameter is ignored when `generator: random` was specified;

- `cases: 1000`
  the (positive) number of cases being simulated;

- `death: ...`
  the `death:` parameter may either be followed by the path to a file (if its initial character is a tilde (~) it is replaced by the user's home directory; if it's a plus (+) it is replaced by the base directory (specified with the `--base` option, see the simrisc(1) man-page)), or it must be followed by 101 cumulative death proportions, where each line starts with `<nr>:`, where `<nr>` is the next order number to read. The default configuration file specifies:

         death:
            1: .00000 .00000 .00000 .00000 .00000 .00000 .00000 .00000 .00000 .00000
           11: .00000 .00000 .00000 .00000 .00000 .00000 .00000 .00000 .00000 .00000
           21: .00000 .00014 .00028 .00042 .00056 .00070 .00106 .00142 .00178 .00214
           31: .00250 .00382 .00514 .00646 .00778 .00910 .01118 .01326 .01534 .01742
           41: .01950 .02312 .02674 .03036 .03398 .03760 .04414 .05068 .05722 .06376
           51: .07030 .07776 .08522 .09268 .10014 .10760 .11564 .12368 .13172 .13976
           61: .14780 .15718 .16656 .17594 .18532 .19470 .20658 .21846 .23034 .24222
           71: .25410 .27560 .29710 .31860 .34010 .36160 .39368 .42576 .45784 .48992
           81: .52200 .56240 .60280 .64320 .68360 .72400 .75826 .79252 .82678 .86104
           91: .89530 .90962 .92394 .93826 .95258 .96690 .97104 .97518 .97932 .98346
          101: .98760

  which are the 101 cumulative death proportions used for breast cancer simulations.

  If the 101 cumulative death proportions are available in, e.g., the user's `.config/` directory as the file `cumdeath` then the specification could have been:

          death:  ~/.config/cumdeath

  which might be convenient when using different values in `Analysis:` specifications (see section `ANALYSES` in the simrisc(1) man-page).

## Section `Costs:' (opt.)

This section may start with a line containing `Costs:` and specifies several parameters used for cost-calculations. Modality-specific cost parameters are specified in Section `Modalities:` (see below). The default configuration file specifies:

- `biop: 176`
  the (positive) cost of performing a biopsy;

- `diameters: 0: 6438 20: 7128 50: 7701`
  pairs of `diameter: cost` values specifying the treatment cost starting at the specified tumor diameter, up to the next pair's diameter (if specified) or all diameters starting at the diameter specified at the last pair. The first diameter must be 0. The second value of each pair specifies the (non-negative) treatment costs for that age-group.

- `Discount: (opt.)`
  the costs discount proportion starting at some age. This line is optional but the followed two additional lines are required: the line `discount:` contains two values specifying, respectively, the discount proportions for breast- and lung-cancer simulations. When only one proportion is specified it represents the proportion of the actually used simulation type (i.e., breast- or lung-cancer); the line `age:` specifies the discount's starting age (for both simulation types). The specified age does not have to be an integral value. A decimal fraction (like 50.5) can also be used. When the used parameters are requested (i.e., when using the `--parameters` option) the age is rounded to two decimals:

          Discount:       # breast    lung
              proportion:      0      .04
              age: 50

## Section `BreastDensities:'

This section starts with a line containing `BreastDensities:` which are used with breast-cancer simulations. It defines breast density values for various age groups, covering ages 0 through the maximum age for simulated cases. The default configuration file contains the following specifications:

        #                  bi-rad:  a       b       c       d
        ageGroup:  0  - 40         0.05    0.30    0.48    0.17
                   40 - 50         0.06    0.34    0.47    0.13
                   50 - 60         0.08    0.50    0.37    0.05
                   60 - 70         0.15    0.53    0.29    0.03
                   70 - *          0.18    0.54    0.26    0.02

Optionally, each line may start with an `ageGroup:` specification, which is required for the first specification line.
Age groups are half-open ranges: starting at their first ages, and ending at (but not including) their second ages.
The first ages of subsequent age groups can be omitted (in which case the group starts at the second age of the previous group) or they must be equal to the second ages of their previous age groups.
For the last age group the specification `*` can be used, indicating that all ages at or above the last age group's begin age are handled by that group. E.g., the above specifications could also have been

        ageGroup:  0  - 40         0.05    0.30    0.48    0.17
                      - 50         0.06    0.34    0.47    0.13
                      - 60         0.08    0.50    0.37    0.05
                      - 70         0.15    0.53    0.29    0.03
                      - *          0.18    0.54    0.26    0.02

Specified ages do not have to be integral values. Decimal fractions (like 40.5) can also be specified. When the used parameters are requested (i.e., when using the `--parameters` option) ages are rounded to two decimals. For each age group the probabilities of the four bi-rad classifications must sum to 1.0.

## Section Modalities: (opt.)

This section may start with a line containing `Modalities:` and specifies cancer-scanning modalities. Currently three modalities are supported for breast-cancer simulations: `Mammo, Tomo, MRI`, and one modality is supported for lung-cancer simulations: `CT`.

Some modalities specify age groups, which are (like the age ranges used for `breastDensities`) half-open ranges: they start at their first ages, and end at (not including) their second-ages, while subsequent age ranges must connect. Also, the last age group may use the end-age specification `*`.

The default configuration file contains (below the line `Modalities:`) the following specifications (if modalities aren't used their specifications are optional):

- `CT:`
  The `CT` modality is used when performing lung cancer simulations. The screening costs are used instead of the value configured at the `Costs: biop:` specification. The `diagnosis:` costs specifies the costs of performing a CT-scan. The `M0` and `M1` values specify the costs when, respectively, no metastatis or a matastasis has been detected.

  The radiation dose of `CT` scans is configured at the `CT: dose:` specification. The sensitivity depends on the tumor diameter. For tumor sizes between 3 and 5 mm. the sensitivity is computed using the formula `(.5 * diameter - 1..5) * 100` (e.g., 50% for tumors of 4 mm.)

  The default configuration file contains the following `CT` specifications:

          CT:
              #        screening    diagnosis    M0      M1   (M0, M1: Table S3)
              costs:      176         1908      37909   56556

              dose:  1

              #               diam.   value (must be integral 0..100 or -1)
              sensitivity:    0 - 3:  0
                              3 - 5:  -1  # formula: (.5 * diam - 1.5) * 100
                              5 - *:  100

              #               mean    stddev  dist
              specificity:    .992    .076    Normal

  Optionally, each `sensitivity` specification line may start with a `sensitivity:` specification, which is required for the first specification line.

- `Mammo:`
  For the `Mammo` modality the costs, radiation doses and m: parameter specifications per bi-rad category, specificity probabilities for age groups, the parameters of the beta-function, and the systematic error probability must be specified.
  The `Mammo` sensitivity is computed using the beta-function published by Isheden and Humphreys (2017, Statistical Methods in Medical Research, 28(3), 681-702). From a randomly generated probability and the case's age the case's bi-rad category is determined and that category is then used to select the m-parameter that is used in the beta-function.
  The default configuration file contains the following `Mammo` specifications:

          Mammo:
              costs:          64

              #      bi-rad:  a       b       c       d
              dose:           3       3       3       3
              m:             .136    .136    .136    .136

              #             ageGroups:
              specificity:  0 - 40:  .961     40 - *: .965

              #       1       2       3        4
              beta:  -4.38    .49     -1.34    -7.18

              systematicError:  0.1

  Specified ages do not have to be integral values and the begin-age of the second age group can optionally be omitted. Decimal fractions (like 40.5) can also be specified. When the used parameters are requested (i.e., when using the `--parameters` option) ages are rounded to two decimals.
- `Tomo:`
  For the `Tomo` modality the costs, radiation doses per bi-rad category, sensitivity probabilities per bi-rad category, and specificity probabilities for age groups must be specified.
  The default configuration file contains the following `Tomo` specifications:

          Tomo:
              costs:         64

              #      bi-rad:  a       b       c       d
              dose:           3       3       3       3
              sensitivity:    .87     .84     .73     .65

              #             ageGroups:
              specificity:  0 - 40:  .961     40 - *: .965

  Specified ages do not have to be integral values and the begin-age of the second age group can optionally be omitted. Decimal fractions (like 40.5) can also be specified. When the used parameters are requested (i.e., when using the `--parameters` option) ages are rounded to two decimals.

- `MRI:`
  For the `MRI` modality the costs, and the sensitivity and specificity probabilities must be specified.
  The default configuration file contains (below the line `MRI:`) the following specifications:

              costs:         280
              #                 proportion:
              sensitivity:      .94
              specificity:      .95

## Section `Screening:' (opt.)

This section may start with a line containing `Screening:` and it specifies the ages at which screenings are performed, the used screening modality/modalities for each of the used screening ages, and the probabilities that screening rounds are attended. If no screening rounds should be used then specify a single round-specification line:

        round: none

Otherwise, the first screening round must start with the keyword `round:` followed by an age, which in turn is followed by a list of at least one space delimited modality specification. Subsequent screening round specifications may optionally start with the keyword `round:`. Currently `Mammo, Tomo, MRI` and `CT` are available. `Mammo, Tomo,` and `MRI` can be specified when performing breast-cancer simulations, `CT` can be specified when performing lung-cancer simulations. The default configuration file contains the following `round` specifications:

        # round:     50  CT
        #            52  CT
        #            54  CT
        #            56  CT
        #            58  CT
        #            60  CT
        #            62  CT
        #            64  CT
        #            66  CT
        #            68  CT
        #            70  CT
        #            72  CT
        #            74  CT

        round:     50  Mammo
                   52  Mammo
                   54  Mammo
                   56  Mammo
                   58  Mammo
                   60  Mammo
                   62  Mammo
                   64  Mammo
                   66  Mammo
                   68  Mammo
                   70  Mammo
                   72  Mammo
                   74  Mammo

The probability that a case will attend a screening round is specified by the `attendanceRate:` parameter:

        #                   probability:
        attendanceRate:     .8

## Section `Tumor:' (opt.)

This section may start with a line containing `Tumor:` and it specifies the characteristics of tumors. Several of the parameters in this section can be varied by specifying `spread: true` in the section `Scenario:`, in which case statistical variations are applied to these parameters.

Supported distributions are `Normal, Uniform, LogNormal,` and (for the lung-cancer's `Beir7` parameters) the `Beta` distribution. If `value` is the specified `value` parameter value, and `spread` the specified `spread` parameter then the values that are actually used during the simulations are:

- when using the `Normal` distribution `N(mean, stddev)`:

         N(value, spread)

- when using the `Uniform` distribution `U(begin, end)`:

         U(value - spread / 2, value + spread / 2)

- when using the `LogNormal` distribution `L(mean, stddev)`:

         L(value, spread)

- the `Beta` distribution is used when requestin lung cancer simulations. For male cases the 95% confidence intervals for the `beta` parameters ranges from .15 to .70, for female cases it ranges from .94 to 2.10, and values drawn from these distributions are used when `spread: true` has been specified (see also section BETA DISTRIBUTIONS).

The `spread` parameters may not be negative. If `spread` values are configured then their distributions must also be specified. If `spread` is not specified, then the `value` parameter won't vary if `spread: true` is specified in the `Scenario` section. The same holds true for the `Beta` distribution: if no spreading should be applied, even though `spread: true` was specified, then the `Beta` distribution's specificatins should be omitted.

The `Tumor:` section has four subsections: `Beir7:, Growth, Incidence:, Survival:,` and `S3:`. They contain the following parameter specifications:

Beir7:

BEIR (tumor induction) parameters: only tumor induction type 7 (i.e., beir7) is used. The default configuration file contains specifications for breast cancer simulations and for male and female lung cancer simulations:

            #    eta   beta  spread   dist.
        breast:  -2.0   0.51   0.32  Normal

        #                            Beta-distribution parameters:
        # LC:    eta   beta  dist    constant factor   aParam    bParam
        male:    -1.4   .32  Beta    .234091  1.72727  2.664237  5.184883
        female:  -1.4  1.40  Beta    .744828   .818966 3.366115  4.813548

If `spread: true` is specified then the actually used `beta` parameters are drawn from their respective distributions.

See also National Research Council. 2006. Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2. Washington, DC: The National Academies Press (https://doi.org/10.17226/11340).

Growth:

Tumor growth specifications consist of three elements: start diameters, self-detect parameterss and doubling time specifications.

The `start` parameters define the start diameters (in millimeters) of emerging tumors used with respectively, breast and lung cancer simulations. The default configuration file specifies

            # breast lung
        start:   5     3

The default configuration file contains the following specifications of the self-detect parameters for breast and lung cancer simulations:

        #selfDetect:      # stdev      mean     spread    dist
      breast:             2.01375     18.5413   2.31637   Normal
      lung:               1.0141      20.8426   1.84043   Normal

Four parameters are used when determining the diameter at which self-detection is possible. These parameters are:

- the standard deviation (`stdev`) used by the lognormal distribution to compute the diameter at which self-detection occurs. This parameter is required and cannot be negative;
- the `mean` (see below) used by the lognormal distribution. This parameter is required and cannot be negative. Its value will vary using the following two parameters if `spread: true` was specified;
- the spread (standard deviation) used by the distribution that is used to vary the mean if `spread: true` was specified. It can be omitted in which case the mean won't vary;
- the distribution used to vary the mean. If the previous parameter is omitted then this parameter must also be omitted.

The actually used self-detect diameter is computed using:

        diameter = L(mean, stdev)

Finally, the `Growth:` subsection also defines tumor doubling times for various age groups when using breast cancer simulations and for all ages when using lung cancer simulations.

Doubling times are computed like the self-detect diameters, i.e., using millimeters and lognormal distributions. Thus, for each age group and for the lung cancer simulation four parameters are specified (of which the final two are optional): the standard deviation of the lognormal distribution, the mean value of the lognormal distribution, and the spread and name of the distribution that is used when `spread: true` was specified.

The age groups (used with breast cancer simulations) must cover ages 0 through the maximum age for simulated cases, and are specified as described at section `BreastDensities:`. The default configuration file contains the following specifications:

        DoublingTime:
            #                    stdev      mean     spread   dist.
            ageGroup:  1 - 50:   1.84043    79.838   1.53726  Normal
                      50 - 70:   1.29693    157.591  1.1853   Normal
                      70 - * :   1.56831    188.67   1.2586   Normal

            #     all ages        stdev     mean     spread   dist.
            lung:                 1.23368   98.4944  2.09594  Normal

Optionally, each `ageGroup` line may start with an `ageGroup:` specification, which is required for the first specification line.

Incidence: (opt.)

For breast cancer simulations three carrier types are supported: `Normal, BRCA1` and `BRCA2`. Each having a probability of occurrence. The probabilities of these carriers must add to 1. In the default configuration file `BRCA1` and `BRCA2` are specified, but their probabilties are set to 0, in which case their specifications can also be removed from configuration files.

Each carrier is identified by name (i.e., when performing breast cancer simulations `Breast:, BRCA1:`, and `BRCA2`; when performing lung cancer simulations: `Male:` and `Female:`) followed by their parameter specifications:

- for breast cancer simulations: the probability that the carrier is observed;
- the lifetime risk: three parameters specifying a probability;
- the mean age: three parameters specifying the mean age,;
- the standard deviation used when computing the risk of getting a tumor. As this standard deviation is used in the denominator of expressions it must be larger than zero.

The lifetime risk, mean age and standard deviation parameters may optionally be followed by the standard deviation (spread) and distribution used to vary the probability when `spread: true` is specified;

The default configuration file contains these specifications:

        Male:
            #                   value   spread  distr.
            lifetimeRisk:         .22   .005    Normal
            meanAge:            72.48  1.08     Normal
            stdDev:              9.28  1.62     Normal

        Female:
            #                   value   spread  distr.
            lifetimeRisk:         .20   .004    Normal
            meanAge:            69.62  1.49     Normal
            stdDev:              9.73  1.83     Normal

        Breast:
            probability:    1
            #                   value   spread  distr.
            lifetimeRisk:         .226  .0053   Normal
            meanAge:            72.9    .552    Normal
            stdDev:             21.1

        BRCA1:
            probability:    0
            #                   value   spread  distr.
            lifetimeRisk:         .96
            meanAge:            53.9
            stdDev:             16.51

         BRCA2:
            probability:    0
            #                   value   spread  distr.
            lifetimeRisk:         .96
            meanAge:            53.9
            stdDev:             16.51

Instead of specifying the parameters of a distribution, a `riskTable` can also be used. If a `riskTable` is specified at a category (i.e., `Male: .. BRCA2:`) then the `lifetimeRisk, meanAge,` and `stdDev` parameters are ignored. A `riskTable` specification contains pairs of values. The first value of a pair specifies an age, the second value the probability of a tumor developing until that age. Both ages and probabilities must be cumulative and at least two pairs must be specified.

Unless specified in the `riskTable` specification itself simrisc adds a pair `0, .00` at the beginning, and an age specification `100` at the end. Its cumulative tumor probability is computed using linear extrapolation of the two age values before age 100, using a maximum value of 1.00. For ages in between pairs of age values linear interpolation is used, using the surrounding age specifications. Here is a (fictitious) example of a `riskTable` specification in the `Male:` category:

        Male:
            riskTable:
                40 .01      50 .1       55 .15      60 .22
                65 .55      70 .62      75 .67

Survival: (opt.)

For breast cancer simulations four types of survival parameters must be specified. Each type (a..d) specifies a mean, and (optionally) a spread and distribution (which are used when `spread: true` has been specified). The default configuration file specifies:

        #              value        spread      dist:
        type:  a        .00004475   .000004392  Normal
               b       1.85867      .0420       Normal
               c       -.271        .0101       Normal
               d       2.0167       .0366       Normal
               e       1.00         .01         Normal

Optionally, each line may start with a `type:` specification, which is required for the first specification line.

The `e` parameters can be used to estimate relative survival if not enough data are available (and can reflect the quality of care). The value 1 indicates that enough data are available to estimate survival using the `a` to `d` parameters. If not enough data are available the `e` parameter can be used to adjust the survival estimate to correct the use of the `a` to `f` parameters to the quality level of the medical care relative to a country for which the `a` to `d` parameters are available. E.g., in Dutch breast cancer research studying the survival in Indonesia the value 0.9 was used since using that factor in combination with the provided `a` to `d` parameter values the correct survival probabilities for Indonesia were obtained.

When performing breast cancer simulations TNM indices (cf. the description of the S3 table below) are also determined. With breast cancer simulations the second TNM value is always 0, and the first TNM value is, as with table S3, determined by the tumor's diameter. The default configuration file contains the following `bc:` specification (see also option `--tnm`):

        #  BC TNM categories thru (<=) diameters (mm):
        bc:        20  50   *
        #  TNM:    T1  T2  T3

(cf. https://www.cancerresearchuk.org/about-cancer/breast-cancer/stages-types-grades/tnm-staging).

For lung cancer simulations table `S4` is used to determine the a..e parameters. Table `S4` contains four categories (lung0..lung3) defining these a..e parameters, where (for a known cancer's diameter) the category is randomly determined using table `S3` (see below).

Table `S4` is appended to the breast cancer specifications. The default configuration file contains the following specifications of table `S4`:

       # table S4: 4 columns per a..d parameter
       # lungX: X is table S4's column index
       lung0: a        .00143      .00095      Normal
              b       1.84559      .33748      Normal
              c       -.22794      .07823      Normal
              d       1.06799      .16226      Normal
              e       1.00         .01         Normal

       lung1: a        .01530      .00381      Normal
              b       1.69434      .10979      Normal
              c       -.19358      .02105      Normal
              d        .66690      .03869      Normal
              e       1.00         .01         Normal

       lung2: a        .78600      .29815      Normal
              b        .69791      .05425      Normal
              c        .0          .0          Normal
              d        .0          .0          Normal
              e       1.00         .01         Normal

       lung3: a       1.25148      .32305      Normal
              b        .77852      .34149      Normal
              c        .0          .0          Normal
              d        .0          .0          Normal
              e       1.00         .01         Normal

Optionally, each subsequent line following the first `lung0: .. lung3:` line may repeat its `lung1: .. lung3:` label.

S3: (opt.)

With lung cancer specifications tables `S3` and `S4` are used to determine the survival parameters. The tumor's diameter determines the row of table S3, and then its column is randomly determined using the probabilities listed in S3's rows. For each row the probabilities must sum to 1. Once the S3 column has been determined the column index which of the `lungX:` specifications is used. The row and column indices are 0-based. E.g., if a tumor diameter is 24, then row 2 (diameter <= 30) is selected. Then, if the random value is .630, column 1 is used (column N1-3,M0). Whenever a tumor is present these pairs of indices are reported in the comma-separated data file in the column marked as `TNM`, using an entry like `2,1`.

The default configuration file contains the following table `S3`:

        S3:
           #      diameter (mm)
           # T-row    <=       N0,M0   N1-3,M0   N1-3,M1a-b   N0-3M1c
           prob:      10:       .756    .157      .048        .039       # T1a,b
                      20:       .703    .197      .055        .045       # T1b
                      30:       .559    .267      .095        .078       # T1c
                      50:       .345    .351      .167        .137       # T2a,b
                      70:       .196    .408      .218        .178       # T3
                       *:       .187    .347      .256        .210       # T4

Optionally, each line may start with a `prob:` specification, which is required for the first specification line.
(cf. https://www.sciencedirect.com/science/article/pii/S2667005421000491 and Table 1 of its appendix: https://ars.els-cdn.com/content/image/1-s2.0-S2667005421000491-mmc1.pdf)

## BETA DISTRIBUTIONS

Values generated from Beta distributions range between 0 and 1 (cf. https://en.wikipedia.org/wiki/Beta_distribution). The Beta distribution is computed using two Gamma distributions (cf. https://www.fmrib.ox.ac.uk/datasets/techrep/tr03tb1/tr03tb1/node24.html, https://stats.stackexchange.com/questions/502146/how-does-numpy-generate-samples-from-a-beta-distribution):

        gamma1 = Gamma(aParam, 1)
        Beta(aParam, bParam) = gamma1 / (gamma1 + Gamma(bParam, 1))

When using lung cancer simulations the 95% confidence interval (CI) for male cases ranges from .15 to .70, with a mean value of .32, and for women ranging from .94 to 2.10 with a mean value of 1.40.

The male and female CI ranges are transformed to .025 to .975 ranges using linear transformations. To transform values `x` from the male range to the .025 to .975 range the transformation `y = 1.72727 * x - .234091` is used, and to transform back the transformation `(y + .234091) / 1.72727` is used. For the female CI the transformations are `y = .818966 * x - .744828` and `(y + .744828) / .818966`.

The `aParam` and `bParam` values are determined by first generating 1000 values so that their CI span the range 0.025 to .975, with a mean value of 0.318635 (for male cases) and 0.401724 (for female cases). Next the parameters of the corresponding beta distribution were estimated using maximum likelihood fitting, resulting in `aParam = 2.664237` and `bParam = 5.184883` for the distribution used with male lungcancer simulations, and `aParam = 3.366115` and `bParam = 4.813548` for the distribution used with female lungcancer simulations.

The default configuration file shows these values at the Beir7 beta parameters.

## PARAMETER RESPECIFICATION

Parameters can be respecified by defining a separate parameter configuration file or by providing alternate parameter specifications in `Analysis:` sections of the program's input file, or by providing alternative parameter specifications as command-line arguments (cf. the simrisc(1) man-page)

## FILES

Configuration files

- `~/.config/simrisc`: the default location of the program's configuration file;
- the simrisc distribution archive contains the default configuration file as `simrisc-VERSION/stdconfig/simrisc`, where `VERSION` is replaced by simrisc's actual release version;
- when installing simrisc using Linux distribution archives (e.g., `.deb` files) the default configuration file is commonly available as `/usr/shared/doc/simrisc/simrisc.gz`

## SEE ALSO

simrisc(1)

## BUGS

Versions before version 15.03.00 should not be used for lung cancer simulations.

## COPYRIGHT

This is free software, distributed under the terms of the GNU General Public License (GPL).

## AUTHOR

Frank B. Brokken (f.b.brokken@rug.nl),