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Problems about take logarithm in two obs. in single variable

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Problems about take logarithm in two obs. in single variable

Can anyone suggest the method for me to me to take logarithm on divided of two observation, e.g. log(VariableX/VariableX[n+1])that like Excel?
Example, =log(A10/A11).
My Constraint is huge amount of data that cannot process in Excel.
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Re: Problems about take logarithm in two obs. in single variable

This question is perhaps best answered by Technical Support. You can enter it online at http://support.sas.com/ctx/supportform/index.jsp .

-- David Kelley, SAS
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Posts: 260

Re: Problems about take logarithm in two obs. in single variable

In SAS, you can't read the value of the next line... but you can use the value of the previous line.
So in a Data step, compute a new variable, the formula of which will be :
LOG(LAG(X)/X) ;

The LAG function returns the value for variable X on the previously read observation.
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