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Re: st: renaming variables from first observation


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: renaming variables from first observation
Date   Thu, 25 Aug 2011 10:27:00 +0100

In fact, much of the last part of this to with -renvars- is a red
herring. I was wondering exactly why my code with -renvars- worked; I
just figured out that it was an accident in the original example in
which buggy code gave the right answer for the wrong reason.

Better code is

renvars , map(word(@[1], 1))

This should be more transparent. The idiosyncratic detail is that @ is
a placeholder for each variable name in turn. The recipe then is to
use the first word of the value in the first observation. So for
-var1- the new name would be the value of

word(var1[1], 1)

Nick

On Thu, Aug 25, 2011 at 10:13 AM, Nick Cox <njcoxstata@gmail.com> wrote:
> Let's assume that your first values are all legal names. You could
> indeed do this
>
> forval j  = 1/14 {
>      local names `names' `=var`j'[1]'
> }
> renvars var1-var14 \ `names'
>
> But that's actually dozens of lines more code (look _inside_ -renvars-)  than
>
> forval j = 1/14 {
>     rename var`j' `=var`j'[1]'
> }
>
> and the second is in any case shorter and more direct, even without
> looking inside -renvars-.
>
> You asked what a solution was with -renvars- and I agree that it looks
> complicated. The -map()- option was mine and intended as an outlet for
> the desperate user-programmer whose problem was not met by any of the
> other options. But usually you need to be moderately fluent in Stata
> to make effective use of it. The program was written for the authors'
> use and any utility beyond that is a pleasant side-effect!
>
> `= exp'
>
> evaluates an expression on the fly and is documented tersely at -help
> macro-. But the main idea is simple. Consider as part of a command
> line
>
> `= 2 + 2'
>
> Stata sees ` ' and so expects something like a macro reference to be
> substituted. But instead of a macro name there is
>
> = 2 + 2
>
> Stata does the calculation on the fly. In this case the result is 4
> and that is what the command would see.
>
> -renvars- is over a decade old now. After that length of time
> StataCorp caught up and the official -rename- is now much versatile in
> Stata 12, although I doubt it has a way to solve your problem without
> a loop. I would be happy to be shown wrong on that.
>
> Nick
>
>
> On Thu, Aug 25, 2011 at 9:50 AM, Abhimanyu Arora
> <abhimanyu.arora1987@gmail.com> wrote:
>> Yes Nick, precisely, my values in the first observation were not
>> legal. What I meant by storing values in a macro was something like a
>> horizontal -levelsof- command. Once I obtain the values in a single
>> macro I thought of simply using your and Jeroen Weesie's -renvars-.
>>
>> But the map option seems not that easy to understand, perhaps because
>> I find `quotes' confusing sometimes. One needs to have a string
>> expression in the parentheses while using the map option but I see
>> that the expression in your example is in `quotes', normally used for
>> macros. Would be really great if you could clarify this fundamental
>> issue.
>>
>> Many thanks
>> Abhimanyu
>>
>>
>> . list in 1
>>
>>     +--------------------------------------------------------------------------------------------------------------------+
>>  1. |        var1 |        var2 |         var3 |         var4 | var5
>> | var6 | var7 | var8 | var9 | var10 | var11 | var12 |
>>     | Series Code | Series Name | Country Code | Country Name | 2000
>> | 2001 | 2002 | 2003 | 2004 |  2005 |  2006 |  2007 |
>>     |---------------------------------------------------------+----------------------------------------------------------|
>>     |                          var13                          |
>>                   var14                           |
>>     |                           2008                          |
>>                    2009                           |
>>     +--------------------------------------------------------------------------------------------------------------------+
>>
>> On Thu, Aug 25, 2011 at 10:35 AM, Nick Cox <njcoxstata@gmail.com> wrote:
>>> Already answered, but not correctly. You could e.g. use the first word
>>> of the first value. This works:
>>>
>>> . l
>>>
>>>     +------------------------------+
>>>     | var1   var2             var3 |
>>>     |------------------------------|
>>>  1. | Frog   Toad   Venomous snake |
>>>  2. |    1      2                3 |
>>>     +------------------------------+
>>>
>>> . renvars , map(`=word("@", 1)')
>>>
>>> . l
>>>
>>>     +------------------------------+
>>>     | Frog   Toad         Venomous |
>>>     |------------------------------|
>>>  1. | Frog   Toad   Venomous snake |
>>>  2. |    1      2                3 |
>>>     +------------------------------+
>>>
>>> Nick
>>>
>>> On Thu, Aug 25, 2011 at 9:25 AM, Abhimanyu Arora
>>> <abhimanyu.arora1987@gmail.com> wrote:
>>>> I caught the mistake, thanks to -set trace on-. 'Code' is the second
>>>> word of my observation of the first variable and of course a variable
>>>> name has to be single worded. But my question on possibility of using
>>>> Nick's -renvars- remains.
>>>> Best regards
>>>> Abhimanyu
>>>>
>>>>
>>>> On Thu, Aug 25, 2011 at 10:07 AM, Abhimanyu Arora
>>>> <abhimanyu.arora1987@gmail.com> wrote:
>>>>> Good morning statalist
>>>>> I would like to rename my variables var1-var14 to the corresponding
>>>>> values from the first observation.
>>>>> I followed the post on
>>>>> http://www.stata.com/statalist/archive/2004-07/msg00009.html and
>>>>> modified it for my purpose.
>>>>>
>>>>> but I got this error
>>>>>
>>>>> . forvalues k = 1/14  {
>>>>>  2.   local newname  = var`k'[1]
>>>>>  3.   ren var`k'  `newname'
>>>>>  4. }
>>>>>
>>>>> Code not allowed
>>>>>
>>>>> Also is it posible to store the values of an observation in a macro?
>>>>> Perhaps I could then use Nick Cox's -renvars-?
>>>>>
>

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