Re: st: Storing error messages as local macros

[Kenneth Shores <kenneth.a.shores@gmail.com>]

Thanks to both! Sarah, your code worked beautifully. I did not know of
strmatch.

best
-Ken

On Tue, Nov 26, 2013 at 5:10 PM, Nick Cox <njcoxstata@gmail.com> wrote:
> Sarah's helpful advice reminds me that I once wrote a helper program
> -isvar-, which is on SSC.
>
> -------------------------------------------------------------------------------------------------------
> help for isvar
> -------------------------------------------------------------------------------------------------------
>
> Filter names into variable names and others
>
>         isvar possiblevarlist
>
>
> Description
>
>     isvar takes a list of names that might name variables in your
> dataset and filters it into a list
>     of those names that are indeed variable names and a list of the others.
>
>     One application of isvar arises when you are moving between
> similar datasets, especially if they
>     are large, but are not sure which variables are defined in which
> dataset. Commands such as
>     describe would fail at the first name not in fact a variable name.
> isvar offers a more direct way
>     to establish existence or non-existence of several possible variables.
>
>
> Saved results
>
>     r(varlist) names of variables in current dataset
>     r(badlist) names that do not correspond to variables in current dataset
>
>
> Examples
>
>     . isvar mpg rep78 rep77
>     . local OKlist "`r(varlist)'"
>     . su `OKlist'
>
>
> Author
>
>     Nicholas J. Cox, Durham University, U.K.
>     n.j.cox@durham.ac.uk
>
>
> Acknowledgements
>
>     This problem was suggested by Amadou Diallo.
>
>
> Also see
>
>     Online:  help for describe; unab
>
> Nick
> njcoxstata@gmail.com
>
>
> On 27 November 2013 00:48, Sarah Edgington <sedging@ucla.edu> wrote:
>> Kenneth,
>> I've used -desc, varlist- for similar tasks where I have multiple files with
>> different permutations of the variables.
>> One way to do this is something like:
>>
>> desc, varlist
>> **create a macro with a space before and after the varlist so you can always
>> match on space[varname]space
>> **otherwise you might have to worry about vars that match substrings of
>> other vars
>> local indata " `r(varlist)' "
>> **you're probably embedding this in another loop so reset the local keeplist
>> in case it isn't empty
>> local keeplist ""
>> foreach keepvar in schoolid distid math read language  {
>>         **for each variable in your list, cycle through and check that it's
>> in the variable list.
>>         **if it is, add it to a keeplist macro
>>         if strmatch("`indata'","* `keepvar' *") local keeplist "`keeplist'
>> `keepvar'"
>> }
>> keep `keeplist'
>>
>>
>> There are probably more elegant solutions but this does get around the issue
>> of having to parse the error messages.
>>
>> -Sarah
>>
>>
>> -----Original Message-----
>> From: owner-statalist@hsphsun2.harvard.edu
>> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
>> Sent: Tuesday, November 26, 2013 4:15 PM
>> To: statalist@hsphsun2.harvard.edu
>> Subject: Re: st: Storing error messages as local macros
>>
>> Interesting question. I don't know a way to store the error message.
>> What you can do is store the code and replay the message at any later time.
>> For example -error 198- replays the message for 198, regardless of whether
>> was the last error.
>>
>> The commands
>>
>> local rc = _rc
>> if `rc' != 0 <whatever>
>>
>> can be compressed to
>>
>> if _rc != 0 <whatever>
>>
>> and indeed to
>>
>> if _rc <whatever>
>>
>> but it remains true that you would need to store non-zero error codes for
>> later use as _rc contains only a code for the last command issued.
>> Nick
>> njcoxstata@gmail.com
>>
>>
>> On 26 November 2013 23:39, Kenneth Shores <kenneth.a.shores@gmail.com>
>> wrote:
>>> Hi stata list-serve:
>>>
>>> Here is a question I have not seen asked. I am importing a large
>>> number of datasets, keeping variables that I want, doing a number of
>>> reshapes and saving the dataset.
>>>
>>> In each of the datasets, there are core variables that are common
>>> across all datasets. However, there are additional variables that I
>>> want that are not common to all datasets. For example, in dataset i,
>>> there is a school identifier, district identifer, reading, language
>>> and math scores. In dataset j, there is a school identifier, district
>>> identifier, reading, and math scores.
>>>
>>> The first command I wish to run is "keep schoolid distid read math
>> language"
>>> This will return an error when I try to bring up dataset j.
>>>
>>> The alternative I use is:
>>> cap keep schoolid distid read math language loc rc = _rc if `rc' != 0
>>> keep schoolid distid read math
>>>
>>> This works, insofar as all datasets look like i and j. However,
>>> dataset k has schoolid, read, and math. Now the new keep command
>>> breaks.
>>>
>>> There are many different permutations of this. Moreover, there are 300
>>> datasets and programming a specific keep command for each one will be
>>> time consuming  (there are also more than 5 variables that I want).
>>>
>>> It seems that I could make use of the error message itself in these
>>> cases. Because the error message informs me about what vars are not
>>> found, I could store those not found vars in a local macro. The final
>>> code would then be something like this:
>>>
>>> local keepvars "schoolid distid math read language"
>>> cap keep `keepvars'
>>> [store error message, parse "vars not found portion"] loc rc = _rc if
>>> `rc'!=0 loc keepvarsalt: subinstr local keepvars "`[parsed error
>>> message]'" ""
>>> keep `keepvarsalt'
>>>
>>> this would be very flexible and would make use of the specificity of
>>> the Stata error message. However, I cannot find any way to store the
>>> error message text. Is it not possible? And if not, are there
>>> solutions to this problem that others are aware of.
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/faqs/resources/statalist-faq/
> *   http://www.ats.ucla.edu/stat/stata/
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/