R.PCHISQ(x,df,lower_tail,log_p)
x: observation
df: the number of degrees of freedom of the distribution
lower_tail: if true (the default), the lower tail of the distribution is considered
log_p: if true, log of the probability is used
This function returns the cumulative distribution function of the chi-square distribution.
A two argument invocation R.PCHISQ(x,df) is exported to OpenFormula as CHISQDIST(x,df).