#### 15.7.9.1 Missing Values for Cell-Defining Variables ¶

For variables that divide tables into cells, per-variable category options, as described in Per-Variable Category Options, determine which data is analyzed. If any of the categories for such a variable would exclude a case, then that case is not included.

As an example, consider the following entirely artificial dataset, in which ‘`x`’ and ‘`y`’ are categorical variables with missing value 9, and ‘`z`’ is scale:

Data List
x | y | z
--- | --- | ---
1 | 1 | 1
1 | 2 | 10
1 | 9 | 100
2 | 1 | 1000
2 | 2 | 10000
2 | 9 | 100000
9 | 1 | 1000000
9 | 2 | 10000000
9 | 9 | 100000000

Using ‘`x`’ and ‘`y`’ to define cells, and summarizing ‘`z`’, by default PSPP omits all the cases that have ‘`x`’ or ‘`y`’ (or both) missing:

    CTABLES /TABLE x > y > z [SUM].

Custom Tables
|  |  |  |  | Sum
--- | --- | --- | --- | --- | ---
x | 1 | y | 1 | z | 1
2 | z | 10
2 | y | 1 | z | 1000
2 | z | 10000

If, however, we add `CATEGORIES` specifications to include missing values for ‘`y`’ or for ‘`x`’ and ‘`y`’, the output table includes them, like so:

    CTABLES /TABLE x > y > z [SUM] /CATEGORIES VARIABLES=y MISSING=INCLUDE.
    CTABLES /TABLE x > y > z [SUM] /CATEGORIES VARIABLES=x y MISSING=INCLUDE.

Custom Tables
|  |  |  |  | Sum
--- | --- | --- | --- | --- | ---
x | 1 | y | 1 | z | 1
2 | z | 10
9 | z | 100
2 | y | 1 | z | 1000
2 | z | 10000
9 | z | 100000

Custom Tables
|  |  |  |  | Sum
--- | --- | --- | --- | --- | ---
x | 1 | y | 1 | z | 1
2 | z | 10
9 | z | 100
2 | y | 1 | z | 1000
2 | z | 10000
9 | z | 100000
9 | y | 1 | z | 1000000
2 | z | 10000000
9 | z | 100000000