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Re: st: egen rowmin rowmax


From   Teresa Dale Nelson <tdale@utdallas.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: egen rowmin rowmax
Date   Sat, 4 Nov 2006 17:30:55 -0600 (CST)

Philipp,

No, I don't get an error code. Instead, the var for egen 
var=rowmin(varlist) is evaluated to zero or missing.  In fact, some of 
the rows have all zeroes; the rest contain some zeroes and a few values 
between 1 and 13.  

I first create a variable called "rowsum" that totals the row, then I 
egen for the min value on the condition that the rowsum is not equal to 
zero.  Yet, the egen (rowmin)  still evaluates to zeroes and missings. 
All "seq*" variables are type byte, containing a value of 0 to 13. 
Here's the code:

bys id: egen rowsum = 
total(seq1+seq2+seq3+seq4+seq5+seq6+seq7+seq8+seq9+seq10+seq11+seq12+seq
13)

egen byte minmath = rowmin(mathseq*) if rowsum~=0

I had initially tried egen rowsum=total(seq1-seq13) but Stata 
interpreted the dash as an operator (minus sign). So I tried using a 
colon and received an "invalid name" error. Then I entered each 
variable separated by a space, e.g. total(seq1 seq2 seq3 ...) and again 
received an "invalid name" error, as though I had streamed all the 
variables together without spaces.  This is why I included the plus 
signs.

Here's the result:
. tab minmath,m

minmath |      Freq.     Percent      Cum.
----------+----------------------------------
          0 |     19,380     99.38       99.38
           . |        121        0.62     100.00
----------+----------------------------------
     Total |     19,501   100.00


Any ideas?
Thanks,
Terri

Philipp Rehm wrote:


>Can you give an example? Is there an error-code? (For example, Are you 
>sure you don't include, say, a string variable in the varlist?)
>
>The following seems to work:
>
>sysuse auto, clear
>egen min=rowmin(price weight turn)
>egen max=rowmax(price weight turn)
>
>list price weight turn min max
>
>HTH,
>Philipp
>
>Teresa Dale Nelson wrote:
>> Hello,
>> Does anyone know why egen's rowmax command would work but its rowmin 
>> would not?  My data have cases that should suffice in either case.
>> Thank you,
>> Terri
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