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Re: st: saving space while recoding


From   sarah plank <sarahkplank@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: saving space while recoding
Date   Sat, 24 Jul 2010 17:58:47 -0500

Oh my gosh, how great!   I copied and pasted my list into the first
example and it is working, I am running it now but I hope it doesnot
break because I dont understand it enough to make changes.  Thanks.

On Sat, Jul 24, 2010 at 4:35 PM, Eric Booth <ebooth@ppri.tamu.edu> wrote:
> <>
>
>
> There are a couple of possibilities here.   First, you can get rid of the 3 -replace- statements with one -recode- statement that does the same thing, e.g.,
>
> ******!
> recode polyclornew (min/44 = -1)  (45=0)  (46/max = 1) (.=.)
> ******!
>
> but this doesn't make managing your long list of recode conditions much easier.  Also,  a warning: note that the -replace- codes in your example will not recode any values between 44 and 45 (such as 44.5)  nor values between 45 & 46.  Given that a lot of the values in the list your provided aren't integers, this might be a concern.
>
> In terms of making your code shorter you might consider using the -cond()- function.  For example,
> **********************!
> sysuse auto, clear
> keep price
> qui g i = cond(price==4099, 0, cond(missing(price), ., (cond(price<4099, -1, 1))))
> sort price
> **********************!
> will recode price around the 4,099 threshold.
> A brief explanation of what this code is doing is probably helpful here:    if price is == 4099 it will recode i to 0.   If not, it will evaluate the  last "cond(missing(price), ., (cond(price<4099, -1, 1)) " part.    Within this last part it will recode i to -1 if price is less than 4099 and i to 1 if price is greater than or equal to 4099 (but it has already recoded to 0 if price is equal to 4099, so it will just recode to 1 if price is greater than 4099 in this case) .  See -help cond- for more.
>
> To make this work with a long list of conditions like the ones you have provided, you could break the list up into macros &/or  use -tokenize- to loop over the pairs of items in your list.  Here are two examples using the -auto.dta- again:
>
>
> **********************!
> //EXAMPLE 1//
>    /*
> This example uses the list if it is formatted as you presented it in your posting--it will make the changes to items 1 (mpg) and 2(23) in the list and then move on the items 3 and 4 in the list and so on to the end
>    */
>
> sysuse auto, clear
> local list  mpg 23  rep78 3 turn 17 weight 2930 length 196
> **
> token `"`list'"'
> di `"`list'"'
>        while "`1'" != "" {
>         di "recode `1' for value `2'"
>          g i`1' = cond(`1'==`2', 0, cond(missing(`1'), ., (cond(`1'<`2', -1, 1))))
>          mac shift 2    //this part increases the macro `1' by 2 to `3'
>        }
> sort mpg
> order *mpg
> **********************!
>
> Alternatively, if your list were organized down a column in a spreadsheet or something, you could add -local- and a macname to each pair of items to be used for the recodes and loop over each condition.
>
> **********************!
> //EXAMPLE 2//
> sysuse auto, clear
>
> **items in your list:
> local one  mpg 23
> local two  rep78 3
> local three turn 17
> local four weight 2930
> local five length 196
>
> foreach x in one two three four five {
>        token ``x''
>        di "``x''"
>        di "recode `1' for value `2'"
>          g i`1' = cond(`1'==`2', 0, cond(missing(`1'), ., (cond(`1'<`2', -1, 1))))
> }
> sort mpg
> order *mpg
> **********************!
>
> ~ Eric
> __
> Eric A. Booth
> Public Policy Research Institute
> Texas A&M University
> ebooth@ppri.tamu.edu
> Office: +979.845.6754
>
>
>
>
>
> On Jul 24, 2010, at 4:22 PM, sarah plank wrote:
>
>> I need to create a recode but save some space in my code.   I have
>> lots of recodes where I am given the variable to recode and the cutoff
>> point over which to recode the variables.  So, given my list of
>> "polyclor 23.4    polyclor2  33.3  pavol 45  genpt  1.11  gnpt  1  on
>> 0  offon 0  offon2 1  got5  66  {+ 670 more items}"  I need to recode
>> them all by their cutoff in the list, so
>>
>> clonevar polyclor2 = polyclornew
>> replace polyclornew = -1 if polychlornew<44
>> replace polyclornew = 0 if polyclornew==45
>> replace polyclornew = 1 if polyclornew>46 & polyclornew!=.
>> tab polyclornew
>>
>> but this is so exhausting for so many values and so long in the
>> do-code.  How can I make this in less space ?
>>
>> *
>> *   For searches and help try:
>> *   http://www.stata.com/help.cgi?search
>> *   http://www.stata.com/support/statalist/faq
>> *   http://www.ats.ucla.edu/stat/stata/
>
>
>
>
>
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
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> *   http://www.ats.ucla.edu/stat/stata/
>

*
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