汇总Stata中每个观测值的一千个变量

Question

I have made a loop that creates a variable, expectedgpa .

So now I have 1,000 variables for each observation, labeled expectedgpa1 , expectedgpa2 ... expectedgpa1000 .

I want to get the average and standard deviation for all the expectedgpa s for each observation.

So if I have this

Joe       1     2    1    2   4
Sally     2     4    2    4   3
Larry     3     3    3    3   3

I want a variable returned that gives

Joe 2
Sally 3 
Larry 3

Any help?

Answer 1

First, for future questions:

Please post code showing what you've tried. Your question shows no research effort.

Second, to clarify the terminology:

You created 1000 variables, each one corresponding to some expected gpa . Each observation corresponds to a different person. You want, as a result, three variables . One with the person's id and another two with the the mean and sd of the gpa (by person). This is my interpretation, at least.

One solution involves reshaping your data:

clear all
set more off

input ///
str5 id exgpa1 exgpa2 exgpa3 exgpa4 exgpa5
Joe       1     2    1    2   4
Sally     2     4    2    4   3
Larry     3     3    3    3   3
end

list

reshape long exgpa, i(id) j(exgpaid)

collapse (mean) mexgpa=exgpa (sd) sdexgpa=exgpa, by(id)

list

Instead of collapse , you can also run by id: summarize exgpa after the reshape , but this doesn't create new variables.

See help reshape , help collapse and help summarize for details.

Answer 2

You should not have created 1000 new variables without a strategy for how you were going to analyse them!

You could also use egen functions rowmean() and rowsd() and keep the same data structure.

A review of working "rowwise" in Stata is accessible at http://www.stata-journal.com/sjpdf.html?articlenum=pr0046