{* *! version 1.0.6  04mar2011}{...}
    {cmd:gammap(}{it:a}{cmd:,}{it:x}{cmd:)}
{p2colset 8 22 26 2}{...}
{p2col: Domain {it:a}:}1e-10 to 1e+17{p_end}
{p2col: Domain {it:x}:}-8e+307 to 8e+307{p_end}
{p2col :}Interesting domain is {it:x} {ul:>} 0{p_end}
{p2col: Range:}0 to 1{p_end}
{p2col: Description:}returns the cumulative gamma distribution with shape
           parameter {it:a}.{p_end}
{p2col: }returns {cmd:0} if {it:x} < 0.{p_end}

{p2col 8 22 22 2:}The cumulative Poisson (the probability of observing {it:k}
or fewer events if the expected is {it:x}) can be evaluated as 
{cmd:1-gammap(}{it:k}{cmd:+1,}{it:x}{cmd:)}. The reverse cumulative (the
probability of observing {it:k} or more events) can be evaluated as 
{cmd:gammap(}{it:k}{cmd:,}{it:x}{cmd:)}. 

{p2col 8 22 22 2:}{cmd:gammap()} is also known as the incomplete gamma
     function (ratio).{p_end}
     
{p2col 8 22 22 2:}Probabilities for the three-parameter gamma distribution
(see {helpb gammaden()}) can be calculated by shifting and scaling
{it:x}; that is, {cmd:gammap(}{it:a}{cmd:,}({it:x} - {it:g})/{it:b}{cmd:)}.
{p_end}
{p2colreset}{...}
