# 5 Working with data

This chapter returns to Pyxplot’s commands for acting on data stored in files. Chapter 3 has already introduced the `plot` command, which draws graphs, but there are also commands for tabulating data to new data files, for computing histograms, for interpolating data, and for taking Fourier transforms.

Section 3.8 has already introduced the options which can be used to select data from particular columns or which satisfy particular criteria: `using`, `index`, `every` and `select`. These options are universal to all of Pyxplot’s commands which operate on data sets. In all cases, data sets can be read from files, sampled from functions, or specified as a colon-separated list of vectors (see Section 6.5.3).

This chapter begins by describing other common features of these commands, before moving on to describe each command in turn. It leaves the details of the `plot` command, which was introduced in Chapter 3, to be described in full detail in Chapter 1.

- 5.1 Input filters
- 5.2 Reading data from a pipe
- 5.3 Including data within command scripts
- 5.4 Special comment lines in data files
- 5.5 Tabulating functions and slicing data files
- 5.6 Function fitting
- 5.7 Datafile interpolation
  - 5.7.1 Two-dimensional interpolation
- 5.8 Fourier transforms
  - 5.8.1 Window functions
- 5.9 Histograms
- 5.10 Random data generation