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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   Sun, 25 Jul 2010 21:14:36 -0500

Now I have a second list given me where there are some ranges instead
of single cutoff points, so for list  "newvar2 22 25  newvar3  33.5
26  newvar9  55.5  100 "  I need to recode values less than first
range point to -1, values between range to zero, and points above the
second range point to 1.  With the replace command, I can do it:
generate var = -1 if newvar2<=22
replace var = 0 if newvar2>=22 & newvar2<=25
replace var = 1 if newvar2>= 25 & newvar2!=.

and I tried to paste this into the code I got earlier but it doesnt work.
gen var = cond(22<=newvar2<=25, 0, cond(missing(newvar2), .,
(cond(newvar2<22, -1, 1))

This gives me all zeros !  How can I edit this code to work with my
new list and make this work in a loop to save space ?





On Sat, Jul 24, 2010 at 5:58 PM, sarah plank <sarahkplank@gmail.com> wrote:
> 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
>> *   http://www.stata.com/support/statalist/faq
>> *   http://www.ats.ucla.edu/stat/stata/
>>
>

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