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st: loop within a loop


From   Steve Nakoneshny <scnakone@ucalgary.ca>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: loop within a loop
Date   Thu, 10 Nov 2011 13:41:04 -0700

Dear Statalist,

I'm working with a dataset of biomarker data. This dataset contains triplicate scores on 16 unique biomarker measures for a total of 48 variables. Each measure has a unique name (obviously) and each scoring of these appends a letter to the end of the varname like this: v1_A v1_B v1_C ... v16_A v16_B v16_C.

Wanting to calculate new variables for min max and mean scores and then order these results relative to each biomarker measure, I thought I would write a loop to do so rather than write ~64 lines of code.

This is what I did:

-start code-

local y v1_ v2_ v3_ v4_ ... v16_
local i 0

foreach x of local y 	{
	local ++i
		egen `x'min = rowmin(`x'A - `x'C)
		egen `x'max = rowmax(`x'A - `x'C)
		egen `x'mean = rowmean(`x'A - `x'C)
		order `x'min `x'max `x'mean, after(`x'C)
}

- end code-

As far as I can tell, the code executes exactly as I wanted and I now have my new variables created and ordered as planned. What is bugging me though is thinking that I could combine the -egen- commands into a loop and nest it into the larger loop.

I suspect that I would first have to create -local a min max mean- and rewrite the -egen- command as -egen `x'`a' = row`a'(`x'A - `x'C)- (and then delete the two superfluous -egen- commands). However, that in and of itself will not be sufficient and I don't know enough to provide the appropriate syntax to have the loop execute correctly. I am still relatively new to using loops and would appreciate some suggestions.

Thanks,
Steve Nakoneshny
scnakone@ucalgary.ca





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