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RE: st: saving space while recoding


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: saving space while recoding
Date   Mon, 26 Jul 2010 14:14:42 +0200

<>
For -irecode- also try
http://www.stata-journal.com/article.html?article=st0181

HTH
Martin

-original message-
Subject: Re: st: saving space while recoding
From: Jeph Herrin <stata@spandrel.net>
Date: 26-07-2010 14:07

You find -irecode- useful:

   gen var = irecode(newvar2,22,25,.)-1


hth,
Jeph

On 7/25/2010 10:14 PM, sarah plank wrote:
> 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:
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>>> *   http://www.ats.ucla.edu/stat/stata/
>>>
>>
>
> *
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>
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