[R] categorical column to numeric column

[ONKELINX, Thierry]

Maybe this isn't the most elegant way, but it should work.
dd$g <- -1
dd$g[dd$aa == "a"] <- 1

Cheers,

Thierry
------------------------------------------------------------------------
----

ir. Thierry Onkelinx

Instituut voor natuur- en bosonderzoek / Reseach Institute for Nature
and Forest

Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance

Gaverstraat 4

9500 Geraardsbergen

Belgium

tel. + 32 54/436 185

Thierry.Onkelinx op inbo.be

www.inbo.be 

 

Do not put your faith in what statistics say until you have carefully
considered what they do not say.  ~William W. Watt

A statistical analysis, properly conducted, is a delicate dissection of
uncertainties, a surgery of suppositions. ~M.J.Moroney

-----Oorspronkelijk bericht-----
Van: r-help-bounces op stat.math.ethz.ch
[mailto:r-help-bounces op stat.math.ethz.ch] Namens Shubha Vishwanath
Karanth
Verzonden: maandag 19 februari 2007 14:36
Aan: r-help
Onderwerp: [R] categorical column to numeric column

Hi R,

 

Let 'dd' be a data frame given as:

 

dd=data.frame(aa=c("a","a","b","a","b","b"),bb=c(1,1,1,2,3,4))

 

Now I want to create a column 'g' such that if dd$aa=a then dd$g=1 else
dd$g= -1 .

 

So, I gave the below syntax:

 

if((dd$aa)=="a") dd$g=1 else dd$g= -1

 

But I get the error message as:

Warning message: 

the condition has length > 1 and only the first element will be used in:
if ((dd$aa) == "a") dd$g = 1 else dd$g = -1 

 

and dd=

 

> dd

  aa bb g

1  a  1 1

2  a  1 1

3  b  1 1

4  a  2 1

5  b  3 1

6  b  4 1

> 

 

Please let me know what is the error I am doing?

 

 

 

 


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