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st: -svmat- with matrix colnames based on factor variable names?
From
<[email protected]>
To
<[email protected]>
Subject
st: -svmat- with matrix colnames based on factor variable names?
Date
Sat, 12 Feb 2011 18:09:09 -0000
[Reposted as original post (12 February 2011 10:50) hasn't appeared in
the Archives]
Thanks to Nick Cox, Austin Nichols and Scott Merryman for their
responses. Scott's message pointed, inter alia, to a useful Statalist
posting by himself, and also to a Stata News article in which graphing
after -margins- is usefully accomplished using Roger Newson's -parmest-
(on SSC). The small, but perhaps important, difference in my case is
that the x-axis variable in my proposed graphs are categorical (factor
variable values) rather than continuous (age in years in the News and
Scott's examples). As Nick and Austin suggest, some pre- or
post-processing of the colnames/factor varlist is inevitable. Austin
kindly offered some assistance were I to suggest an example based on
public data. Here's one inspired by Scott's earlier example [I've added
use of variable hsizgp, which is categorical taking values 1(1)5]:
. webuse nhanes2f, clear
. logit diabetes i.hsizgp i.black i.female age i.female#c.age, nolog
Logistic regression Number of obs =
10335
LR chi2(8) =
391.83
Prob > chi2 =
0.0000
Log likelihood = -1803.1523 Pseudo R2 =
0.0980
------------------------------------------------------------------------
------
diabetes | Coef. Std. Err. z P>|z| [95% Conf.
Interval]
-------------+----------------------------------------------------------
------
hsizgp |
2 | -.1797069 .1280784 -1.40 0.161 -.4307359
.0713221
3 | .11717 .1621709 0.72 0.470 -.2006792
.4350192
4 | .3391857 .1847375 1.84 0.066 -.0228931
.7012645
5 | -.0473484 .1967049 -0.24 0.810 -.4328829
.3381862
|
1.black | .6699473 .1286628 5.21 0.000 .4177728
.9221217
1.female | 1.435121 .489943 2.93 0.003 .4748507
2.395392
age | .0766945 .0066901 11.46 0.000 .063582
.0898069
|
female#c.age |
1 | -.0213554 .0079371 -2.69 0.007 -.0369117
-.005799
|
_cons | -7.403102 .4346565 -17.03 0.000 -8.255013
-6.551191
------------------------------------------------------------------------
------
. margins , at(female = 1 age = 40 hsizgp = (1(1)5) ) post
Predictive margins Number of obs =
10335
Model VCE : OIM
Expression : Pr(diabetes), predict()
1._at : hsizgp = 1
female = 1
age = 40
2._at : hsizgp = 2
female = 1
age = 40
3._at : hsizgp = 3
female = 1
age = 40
4._at : hsizgp = 4
female = 1
age = 40
5._at : hsizgp = 5
female = 1
age = 40
------------------------------------------------------------------------
------
| Delta-method
| Margin Std. Err. z P>|z| [95% Conf.
Interval]
-------------+----------------------------------------------------------
------
_at |
1 | .0250719 .0038488 6.51 0.000 .0175283
.0326154
2 | .0210404 .002844 7.40 0.000 .0154662
.0266145
3 | .0280953 .0041529 6.77 0.000 .0199558
.0362348
4 | .0348208 .0053377 6.52 0.000 .0243591
.0452825
5 | .023942 .0040474 5.92 0.000 .0160092
.0318748
------------------------------------------------------------------------
------
. matrix at = e(at)
. mat li at
at[5,10]
1b. 2. 3. 4. 5. 0b. 1. 0b.
1.
hsizgp hsizgp hsizgp hsizgp hsizgp black black female
female age
r1 1 0 0 0 0 . . 0
1 40
r2 0 1 0 0 0 . . 0
1 40
r3 0 0 1 0 0 . . 0
1 40
r4 0 0 0 1 0 . . 0
1 40
r5 0 0 0 0 1 . . 0
1 40
. matnames at // -matnames- from SSC (by Austin Nichols)
. di r(c)
`":1b.hsizgp"' `":2.hsizgp"' `":3.hsizgp"' `":4.hsizgp"' `":5.hsizgp"'
`":0b.black"' `":1.black"' `":0b.female"' `":1.female"' `":age"'
. svmat at
. de at*
storage display value
variable name type format label variable label
------------------------------------------------------------------------
----------------------------------------------------------------
at1 float %9.0g
at2 float %9.0g
at3 float %9.0g
at4 float %9.0g
at5 float %9.0g
at6 float %9.0g
at7 float %9.0g
at8 float %9.0g
at9 float %9.0g
at10 float %9.0g
. matrix at2 = e(at)
. svmat at2, name(col)
invalid syntax
r(198);
The workaround I was seeking was a quick/easy/automated way of going
from what is shown as the contents of r(c) after -matnames- to a list of
valid variable names that preserves the essential information. The new
list can be used to re-label the matrix prior to -svmat-. The new names
could be based, for instance, on the old ones but drop the ":" and "."
from the elements of r(c), and add some prefix ("_", say) to each of the
elements. My efforts using -subinstr- and also regular expression
functions were not productive, but that is probably a comment on my
skills.
Thanks, Stephen
------------------------------
Date: Fri, 11 Feb 2011 13:02:58 -0600
From: Scott Merryman <[email protected]>
Subject: Re: st: -svmat- with matrix colnames based on factor variable
names?
On Fri, Feb 11, 2011 at 11:22 AM, <[email protected]> wrote:
> I'm having difficulty using a list of factor variable names to
construct
> the column names of a matrix post-estimation.
>
> This arises when using -margins, over(.)- with multiple -at(.)-
options.
> I want to collect to collect all the estimates in a matrix with one
row
> per at/over combination, with additional columns also containing
values
> for the at values chosen. To keep track, I want the column names for
the
> additional at columns to contain names that identify the factor
> variables.
>
> Overall aim: once I have created the summary matrix , I want to
convert
> each of the columns to a variable, with all the at variables --
together
> with other variables containing estimates and SE -- to be saved to a
> separate mini-dataset, and used for graphing or table processing.
Perhaps the thread "Graphic displays or results from margins" at:
http://www.stata.com/statalist/archive/2010-09/msg00807.html
or the example in the vol 25 number 3 of The Stata News (
http://www.stata.com/news/statanews.25.3.pdf ) would be useful.
Scott
===============
From: Austin Nichols <[email protected]>
Subject: Re: st: -svmat- with matrix colnames based on factor variable
names?
Stephen--
Why do you need the names option on -svmat-? You can also write a
little loop to save the matrix to variables/obs on your data, without
putting illegal names on variables. But either way, you will have to
figure out what you want to call a variable that wants to be named
0b.edlevel or whatever.
If you provide an example with public data, I will come up with a few
solutions for you.
===============
------------------------------
Date: Fri, 11 Feb 2011 18:13:36 +0000
From: Nick Cox <[email protected]>
Subject: st: RE: -svmat- with matrix colnames based on factor variable
names?
I don't have a positive solution but I do note -svmat- was written for
version 4 and so it is indeed unlikely to support factor variables. So
any pre-processing for -svmat- would have to find a work-around for
that.
Nick
[email protected]
+++++++++++++++
Stephen
-------------------------------------
Professor Stephen P. Jenkins <[email protected]>
Department of Social Policy and STICERD
London School of Economics and Political Science
Houghton Street
London WC2A 2AE, U.K.
Tel. +44 (0)20 7955 6527
Survival Analysis using Stata:
http://www.iser.essex.ac.uk/survival-analysis
Downloadable papers and software: http://ideas.repec.org/e/pje7.html
Please access the attached hyperlink for an important electronic communications disclaimer: http://lse.ac.uk/emailDisclaimer
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