Thanks Nick! It is very helpful!
I tried your suggestion -- 4-line code for general case, where I changed
rowsof(b) to colsof(b) and get the result correctly.
Phil and Feiveson,
Thanks for contributing your solutions. I will try them all.
Lei
-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
Sent: Thursday, May 18, 2006 12:07 PM
To: statalist@hsphsun2.harvard.edu
Subject: RE: st: right shift elements in a matrix
I think we can all agree that -svmat-
is not especially helpful here.
Alternatively, consider some retro-chic
or retro-not-so-chic solutions.
For a row vector with 4 elements,
mat b = e(b)
mat b = b[1,4], b[1,1..3]
More generally,
mat b = e(b)
local R = rowsof(b)
local r = `R' - 1
mat b = b[1,`R'], b[1,1..`r']
Yet more generally, check out the ancient
-matselrc- published in STB-56 in 2000.
. search matselrc
will point to downloadable code.
-matselrc- fixes the column names as
well, which the interactive code
above does not do.
Nick
n.j.cox@durham.ac.uk
Phil Schumm
> On May 18, 2006, at 9:55 AM, Lei Xuan wrote:
> > After logistic regression (-logit-), I have a parameter matrix e(b).
> > Let
> > matrix b=e(b)
> > N=e(df_m)+1 (number of independent variables plus 1)
> >
> > we have
> > b[1,1] b[1,2] ... b[1,N]
> >
> > I want to generate a new matrix with the same elements but
> > different order
> > (shift one element right), that is,
> >
> > b[1,N], b[1,1], b[1,2], ..., b[1, N-1]
>
>
> Here is a Mata-based solution to your immediate question:
>
>
> cap mata: mata drop shift_columns()
> mata:
> void shift_columns(string scalar old_mat, string scalar new_mat) {
> real matrix m
> real rowvector v
>
> m = st_matrix(old_mat)
> v = cols(m), (1..cols(m)-1)
>
> st_matrix(new_mat, m[.,v])
> st_matrixrowstripe(new_mat, st_matrixrowstripe(old_mat))
> st_matrixcolstripe(new_mat, st_matrixcolstripe(old_mat)[v,.])
> }
> end
>
> mat b = e(b)
> mata: shift_columns("b", "foo")
> mat li foo
>
>
> Note that the first line is required if you put this into a do-file
> and run it multiple times within the same Stata session; without it,
> the second run would throw an error because the function
> shift_columns
> () has already been defined.
>
> I presume that this step is just part of a larger problem you are
> trying to tackle. If so, depending upon what that problem is, this
> might not be the optimal solution.
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