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Re: st: variable names in matrix


From   daniel klein <klein.daniel.81@googlemail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: variable names in matrix
Date   Tue, 10 May 2011 00:53:27 +0200

Stefan,

there are several problems with your code. Firstly,

"mat A=J(1,2,.)"

will not work, because in your example your matrix A has 3 rows, not
only 1. Secondly you do not need 2 colums, because, as you have
already pointed out, a matrix may not conatin strings. But see -help
mat rownames- for an alternative.

"scalar aaa=sum(`var')
mat A=(A \ ??? , aaa)"

will also not do what you probably expect it to do. Firstly -sum()-
returns the runnig sum of a variable. You are probably looking for
-total()-, an -egen- function. Secondly, within a loop you want to
code something like
. mat A[`i', 1] = x

Please see -help matrix-.

Here are two rather ad hoc solutions:

/*---example 1---*/
tempvar s
unab vars : *
mat A = J(`: word count `vars'', 1, .)
mat rownames A = `vars'
loc i 0
foreach v in `vars' {
   qui g `s' = sum(`v')
   mat A[`++i', 1] = `s'[_N]
   drop `s'
}

matlist A
/*---end---*/

/*---example 2---*/
mata :
   A = .
   st_view(A, ., .)
   st_matrix("A", colsum(A)')
end
unab nams : *
mat rownames A = `nams'

matlist A
/*---end---*/
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