dnchisq(x, df) pnchisq(x, df) qnchisq(x, df) rnchisq(x, df)
df degrees of freedom.
dnchisq gives the density, pnchisq gives the
distribution function qnchisq gives the quantile
function and rnchisq generates random deviates.
The non-central chi-square distribution with n degrees-of-freedom has density
f(x) = 1 / (2^(n/2) Gamma(n/2)) x^(n/2-1) e^-x/2