Much of our hard work has already been done by Nick Cox (ofcourse).
See:
-findit ds3-. Once you installed that program you can run the example
below:
*------- begin example -----------
sysuse auto, clear
ds3 , all(X==0 | missing(X))
if "`r(varlist)'" != "" {
drop `r(varlist)'
}
*-------- end example ------------
Hope this helps,
Maarten
--- Maarten Buis <[email protected]> wrote:
> Here is a program that'll do what you want (and more). Save the
> program in a separate file called conddropvar.ado on your hard disk.
> In the example change the -cd- command to point to the folder in
> which you stored conddropvar.ado.
>
> Hope this helps,
> Maarten
>
> *----------- begin program -------------
> *! 1.0.0 MLB 6 Jul 2007
> program define conddropvar, rclass
> syntax [varlist] [if] [in] [aweight fweight iweight] , ///
> [ ///
> ALLOBS(string) ///
> MINVAR(numlist>=0 max=1) ///
> MINVALUES(numlist>0 integer max=1) ///
> STROK ///
> IGNORESTR ///
> REPLACE ///
> ]
>
> marksample touse, strok
> qui count if `touse'
> local N = r(N)
> if `N' == 0 {
> di as error "no observations"
> exit 2000
> }
>
> if "`weight'" != "" {
> local wgt "[`weight'`exp']"
> }
>
> if `"`allobs'`minvar'`minvalues'"' == "" {
> di as error "at least one of the options allobs, minvar, and
> minvalues"
> di as error "must be specified"
> exit 198
> }
>
> if `"`strok'"' != "" & `"`minvar'"' != "" {
> di as error "options strok and minvar cannot be combined"
> exit 198
> }
>
> if "`strok'" != "" & "`ignorestr'" != "" {
> di ass error "options strok and ignorestr cannot be combined"
> exit 198
> }
>
> if "`ignorestr'" != "" {
> qui ds `varlist', not(type string)
> local varlist "`r(varlist)'"
> }
>
> if `"`allobs'"' != "" {
> if "`strok'" != "" {
> capture confirm string variable `varlist'
> if _rc {
> di as error "All variables in varlist must be strings"
> di as error "if both the strok and allobs options are specified"
> exit 198
> }
> }
> if "`strok'`ignorestr'" == "" {
> capture confirm numeric variable `varlist'
> if _rc {
> di as error "No variable in varlist may be a string"
> di as error "if the option allobs is specified and"
> di as error "neither the options strok or ignorestr are
> specified"
> exit 198
> }
> }
> }
>
>
> if `"allobs"' != "" {
> gettoken var : varlist
> local cond : subinstr local allobs "var" "`var'", all
> capture sum `var' if `cond' & `touse'
> if _rc > 0 {
> di as error "`allobs' is not a valid condition"
> exit 198
> }
> }
>
>
> if `"`minvalues'"' != "" {
> tempvar first sort
> gen long `sort' = _n
> gen byte `first' = 0
> }
>
> foreach var of varlist `varlist' {
> local drop = 0
> if `"`allobs'"' != "" {
> local cond : subinstr local allobs "var" "`var'", all
> qui count if (`cond') & `touse'
> if r(N) == `N' local drop = 1
> }
> if `"`minvar'"' != "" {
> qui sum `var' `wgt' if `touse'
> if r(Var) < `minvar' local drop = 1
> }
> if `"`minvalues'"' != "" {
> qui replace `first' = 0
> qui bys `var' `touse' : replace `first' = 1 if _n == 1 & `touse'
> qui count if `first'
> if r(N) < `minvalues' local drop = 1
> }
> if `drop' == 1 local todrop "`todrop' `var'"
> }
> local todrop : list retokenize todrop
>
> if "`replace'" == "" {
> di as txt "the replace options was not specified so the data remain
> unchanged"
> di
> if "`todrop'" != "" {
> di as txt "If the replace option was also specified"
> di as txt "the following variables would have been dropped: "
> di as result "`todrop'" as txt "."
> di
> di as txt "To drop those variables repeat this command with the
> replace option."
> }
> else {
> di as txt "No variable would have been dropped"
> di as txt "if the replace option was specified."
> }
> return local todrop "`todrop'"
> }
> if "`replace'" != "" {
> if "`todrop'" != "" {
> di as txt "The following variables have been dropped: "
> di as result "`todrop'" as txt "."
> drop `todrop'
> }
> else {
> di as txt "No variable has been dropped"
> }
> }
> if "`minvalues'" != "" {
> sort `sort'
> }
> end
> *------------------ end program -----------------
>
> *---------------- begin example ---------------
> set more off
> local home "h"
> cd "`home':\mijn documenten\projecten\stata\conddropvar"
> sysuse auto, clear
> *set trace on
> conddropvar , allobs("var==0 | missing(var)") ignorestr
> *set trace on
> conddropvar , allobs("var==0 | var==1") minvalues(6) ignorestr
> replace
> exit
> *-------------------- end example -------------------
>
> -----------------------------------------
> Maarten L. Buis
> Department of Social Research Methodology
> Vrije Universiteit Amsterdam
> Boelelaan 1081
> 1081 HV Amsterdam
> The Netherlands
>
> visiting address:
> Buitenveldertselaan 3 (Metropolitan), room Z434
>
> +31 20 5986715
>
> http://home.fsw.vu.nl/m.buis/
> -----------------------------------------
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Guillermo
> Villa
> Sent: vrijdag 6 juli 2007 16:22
> To: [email protected]
> Subject: st: RE: Drop variables satisfying a condition
>
> Hi,
>
> Thanks, but I think the loop does not work with strings, so it stops
> when it
> finds the first string in the dataset. Do you think it is possible to
> write
> a similar loop for any variable format? I have a huge dataset, with
> about
> 500 variables, so this will be very helpful.
>
> Thanks again.
>
> Guillermo
>
> -----Mensaje original-----
>
=== message truncated ===
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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