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st: RE: RE: efficiently creating 1/0 variables from existing string y/n variables


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: efficiently creating 1/0 variables from existing string y/n variables
Date   Mon, 28 Sep 2009 11:14:22 +0100

In addition, -multencode- from SSC offers a way to -encode- several
string variables at once, with the key twist that the same set of value
labels is used throughout. 

Nick 
n.j.cox@durham.ac.uk 

Martin Weiss

-replace-ing these variables with numeric counterparts would require you
to
change the -type- from string to numeric as well. I think the best way
to do
this for many variables is to employ a loop over them, and have the old
ones
-drop-ped automatically...


**************
clear*

input  str1 alc_now   
 y
 y
 y
 y
 y
 y
 n 
 y          
end

clonevar alc_now1=alc_now
clonevar alc_now2=alc_now
clonevar alc_now3=alc_now

qui ds, has(type string)

foreach var in `r(varlist)'{
		encode `var', gen(`var'_new)
		drop `var'
}

list, noobs


**************
Michael McCulloch

I have a long list of string variables which contain only "y", "n", or  
are missing.
I'm converting them to new numeric variables with values 1 if  the old  
variable is "y", and 0 if "n".
For example:
	gen etoh_now=alc_now=="y"

This gives, correctly:
.. list alc_now etoh_now, clean
        alc_now   etoh_now
   1.         y          1
   2.         y          1
   3.         y          1
   4.         y          1
   5.         y          1
   6.         y          1
   7.         n          0
   8.         y          1

Is there a more efficient way to do this, where I can change "y" to 1  
and "n" to 0 without creating a new variable and manually dropping the  
old variable?

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