## CHISQR_PDF

The CHISQR_PDF function computes the probability P that, in a Chi-square distribution with Df degrees of freedom, a random variable X is less than or equal to a user-specified cutoff value V .

This routine is written in the IDL language. Its source code can be found in the file ``` chisqr_pdf.pro``` in the ``` lib``` subdirectory of the IDL distribution.

### Calling Sequence

Result = CHISQR_PDF( V, Df )

### Arguments

#### V

An integer, single-, or double-precision floating-point scalar that specifies the cutoff value.

#### Df

A positive integer, single- or double-precision floating-point scalar that specifies the number of degrees of freedom of the Chi-square distribution.

### Examples

Use the following command to compute the probability that a random variable X, from the Chi-square distribution with three degrees of freedom, is less than or equal to 6.25. The result should be 0.899939.

result = CHISQR_PDF(6.25, 3)

PRINT, result

IDL prints:

0.899939

Compute the probability that a random variable X from the Chi-square distribution with three degrees of freedom, is greater than 6.25. The result should be 0.100061.

PRINT, 1 - chisqr_pdf(6.25, 3)

IDL prints:

0.100061