# pdf Files

Documentation/UserGuide/PDF Files

Contain a pdf (probability distribution function) of selected variables as a formatted table (essentially a .tab file). A variety of statistics are computed, including the mean and variance of the distribution, the average and standard deviation, and the skewness and kurtosis of the distribution.

A new sequentially numbered
file is created whenever the integration time exceeds an integer multiple of `<output>/dt`

. At the end of execution, the lesser of `tlim/dt`

or `<time>/nlim`

sequentially numbered files will be created. Also writes a
history-type file with name `prb_stat`

.*id*, where *id* is the string identifier for this output, with each row in the file
containing statistics of each .pdf output.

This is a specialized format that is useful only for some problems, where the statistics of fluctuations in some variable is important (for example, 3D turbulence).

An example of an `<output>`

block which creates a pdf of the density is given below.

```
<output2>
out_fmt = pdf # Binary data dump
out = d # density
id = d # string identifier
dt = 1.0 # time increment between outputs
```

Created by the function output_pdf.c; this function should be studied carefully to understand more about this format and what information it contains.