## definite integral in sas

Occasional Contributor
Posts: 18

# definite integral in sas

Hi Everybody,

Could you help me to integrate this function using sas.

integrate x^2 e^(-x/2) between  0 to x and equate the result to 0.95 to find the value of x.

Posts: 3,040

## Re: definite integral in sas

As far as I know, SAS does not evaluate integrals in general. It can perform numerical approximations to your integral, but I don't think there's a procedure or function in SAS to do that, you would have to write it yourself.

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Paige Miller
Occasional Contributor
Posts: 18

## Re: definite integral in sas

Is there a function to find the 95% confidence interval for Gamma Distribution ?

Ram

Posts: 3,040

## Re: definite integral in sas

The GAMINV function will return quantiles from a Gamma Distribution; you would have to make use of the quantiles to create the confidence interval.

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Paige Miller
SAS Super FREQ
Posts: 4,242

## Re: definite integral in sas

As Paige Miller says, you can use the QUANTILE function to find x such that P(t<=x)=0.95.

In general, you can use the QUAD routine in SAS/IML to solve integrals: How to numerically integrate a function in SAS - The DO Loop

It is also worth pointing out that you can evaluate integrals as part of a root-finding or optimization routine. For example, see

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