# Inverse of the survival function¶

chdtri(k, y)

Finds the Chi-square argument x such that the integral from x to infinity of the Chi-square density is equal to the given cumulative probability y.

Parameters: k (int) – degrees of freedom y (float) – cumulative probability

## Description¶

This is accomplished using the inverse gamma integral function and the relation:

x/2 = igami(k/2, y)


## Accuracy¶

See igami() for accuracy.

## Error messages¶

message condition value returned
chdtri domain y < 0 or y > 1 0
k < 1