Hello once again,
I've forgoten my own command syntax, it should be:
desmat: logistic siweekT2 age10yy2, desrep(exp)
There's an example on this in the help file although I suppose you do
have to know where to find it.
As for the speed problems, I'm mystified. I just tried a dataset with
20375 cases and 238 variables and that was no problem (although I did
have to increase matsize and memory). You might want to try desmat as
a command, see if that sheds some light on the problem:
desmat age10yy2
logistic siweekT2 _x_*
desrep, exp
drop _x_*
Of course, if you already have an alternative solution then there's
no need to waste any more time, but I'm curious about this speed
problem with desmat. Pretty strange.
John Hendrickx
--- Roger Harbord <[email protected]> wrote:
Hi John,
I've just installed the latest version of desmat available on SSC -
Distribution-Date: 20011111. (I had the STB-61: dm73.3 version
before.)However an -exp- option still doesn't exist:
. desmat: logistic siweekT2 age10yy2, exp
exp invalid
r(198);
. which desmat
c:\ado\stbplus\d\desmat.ado
*! version 3.0, 30Mar2001, [email protected]
And I'm not including any continuous covariates - only a single
categorical
one with 6 categories at present. -desmat- takes around 2 minutes
even if
I give an outcome variable that doesn't exist so that all it gives
is an
error message to that effect. (If given a non-existent covariate
it
complains straight away though.)
I suppose I could drop all those variables corresponding to
questions that
we're not using (data is results of a survey with a *long*
questionnaire)
but that would be some extra work to create and maintain a 'keep
list' of
variables I'm actually interested in.
Roger.
--On 03 October 2002 04:33 -0700 John Hendrickx
<[email protected]>
wrote:
> Hi Roger,
>
> -desmat- should add a few seconds to your calculations but two
> minutes is way too much. One explanation might be that a
continuous
> variable wasn't specified as such, then -desmat- will create
dummies
> for all 100+ categories and estimation will take a long time. Let
me
> know if -desmat- really slows things down that much on a large
> dataset, maybe it would be worthwhile to create a lite version.
>
> As for exponential coefficients, use the -exp- option,
>
> desmat: logistic y x, exp
>
> will give the same results as
>
> xi: logistic y i.x
>
> -logistic- prints exponential coefficients but saves them as
> loglinear values.
>
> Good luck,
> John Hendrickx
>
> --- Roger Harbord <[email protected]> wrote:
>> What I was really after in the end was similar to the output of
>> e.g.
>> . xi: logistic y i.x
>> . reformat, eform
>>
>> - but with the coefficients labelled using the value labels
>> assigned to x.
>> -desmat- does achieve this, but I had a couple of different
>> problems when I
>> tried -desmat-:
>>
>> 1) It takes over 2 minutes to run the first univariable logistic
>> regression
>> with -desmat- on my data , when -xi- is seemingly instant. May
be
>> connected to the fact that my dataset has 1100 variables (and
2400
>> observations). Much quicker subsequently though, even run on
>> different
>> variables.
>>
>> 2) I can't see how to get -desmat- to exponentiate the
coefficients
>> (to
>> give odds ratios with logistic regression) when used as a
command
>> prefix:
>>
>> . desmat: logistic y i.x
>>
>> gives the same output as:
>>
>> . desmat: logit y i.x
>>
>> - and there's no -eform- option as there is with -outreg- and
>> -reformat-.
>>
>> Also I think -reformat- or -outreg- give me more flexibility in
>> deciding
>> what I want in the output, so I don't need to do so much work on
>> the output
>> before I present it to my client, which is ultimately my aim.
>>
>> In conclusion i'll probably use Nick's 'canned solution' for
>> transferring
>> value labels to variable labels of dummies, in combination with
>> -reformat-
>> or -outreg-. But maybe it would be nice if there was an option
for
>> -xi- to
>> tell it to inherit the labels in this way. Put that on the wish
>> list for
>> Stata 8...
>>
>>
>> Roger.
>> ----------------------------------------------------
>> Roger Harbord mailto:[email protected]
>> Department of Social Medicine, University of Bristol
>>
>>
>>
>> --On 03 October 2002 09:33 +0100 Nick Cox <[email protected]>
>> wrote:
>>
>> > John Hendrickx
>> >
>> >> -desmat- will do this. Try -ssc describe desmat-
>> >
>> > I tried -desmat- after my posting. I couldn't
>> > see that it did quite this.
>> >
>> > Example:
>> >
>> >
>>
>
----------------------------------------------------------------------
>> > -------------------------------------
>> > log: C:\Stata7\desmat.log
>> > log type: text
>> > opened on: 3 Oct 2002, 09:30:21
>> >
>> > . u auto
>> > (1978 Automobile Data)
>> >
>> > . desmat : regress mpg foreign
>> >
>>
>
----------------------------------------------------------------------
>> > ---------
>> > regress
>> >
>>
>
----------------------------------------------------------------------
>> > ---------
>> > < snip >
>> >
>>
>
----------------------------------------------------------------------
>> > ---------
>> > nr Effect
>> Coeff
>> > s.e.
>> >
>>
>
----------------------------------------------------------------------
>> > ---------
>> > foreign
>> > 1 Foreign
>> 4.946**
>> > 1.362
>> > 2 _cons
>> 19.827**
>> > 0.743
>> >
>>
>
----------------------------------------------------------------------
>> > ---------
>> > * p < .05
>> > ** p < .01
>> >
>> > . d _x_1
>> >
>> > storage display value
>> > variable name type format label variable label
>> >
>>
>
----------------------------------------------------------------------
=== message truncated ===
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