R help - Dec 2010 - Changing names of a string variable

Hello,
Here is the data set I am working with:
dat=read.csv('http://dl.dropbox.com/u/1852742/relexpressions.csv')
names(dat)

#Under the 'target' column, I want to change all of the values into
all capital letters (e.g. fgf2 becomes FGF2).  I have taken a loop
approach but I think my Python background is confusing me.  Here is
what I attempted:

for(line in dat[,1]){if(line=='fgf2'){line<-'FGF2'}}
#I made sure that it was looping through each line by entering:
for(line in dat[,1]){if(line=='fgf2'){print(line)}} #Which did exactly
what I thought it would.

#This doesn't change anything, though.  Also, after reading the
documentation I am still confused how to add multiple "if"
statements.  I would need that because I need to change the names of
fgf2, fgf7, and fgf10.

#I am sure there is a built-in function to do what I need, but I
haven't found it yet so I tried this loop method.  Any help is greatly
appreciated!

Jahan

Hello,

To do what you want, see ?toupper :

levels(dat$target) <- toupper(levels(dat$target))

However, for clarity,

dat$target is not a "string variable", it is a factor,
which you can verify with

 > str(dat)

Factors are enumerated types, and have a discrete
set of 'levels' associated with them,
which can be queried with the ?levels function.

'Behind the scenes', R is storing this variable
as numeric codes, not the character string associated
with each numeric code.

This contrasts with character vectors.


--Erik

Jahan wrote:
> Hello,
> Here is the data set I am working with:
> dat=read.csv('http://dl.dropbox.com/u/1852742/relexpressions.csv')
> names(dat)
> 
> #Under the 'target' column, I want to change all of the values into
> all capital letters (e.g. fgf2 becomes FGF2).  I have taken a loop
> approach but I think my Python background is confusing me.  Here is
> what I attempted:
> 
> for(line in dat[,1]){if(line=='fgf2'){line<-'FGF2'}}
> #I made sure that it was looping through each line by entering:
> for(line in dat[,1]){if(line=='fgf2'){print(line)}} #Which did
exactly
> what I thought it would.
> 
> #This doesn't change anything, though.  Also, after reading the
> documentation I am still confused how to add multiple "if"
> statements.  I would need that because I need to change the names of
> fgf2, fgf7, and fgf10.
> 
> #I am sure there is a built-in function to do what I need, but I
> haven't found it yet so I tried this loop method.  Any help is greatly
> appreciated!
> 
> Jahan
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Jahan -
    Try

dat$target = toupper(dat$target)

I would not recommend a loop for something 
like this.

(You might also want to brush up on your python,
because what you're trying doesn't work in 
python either.)

 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu




On Tue, 7 Dec 2010, Jahan wrote:
> Hello,
> Here is the data set I am working with:
> dat=read.csv('http://dl.dropbox.com/u/1852742/relexpressions.csv')
> names(dat)
>
> #Under the 'target' column, I want to change all of the values into
> all capital letters (e.g. fgf2 becomes FGF2).  I have taken a loop
> approach but I think my Python background is confusing me.  Here is
> what I attempted:
>
> for(line in dat[,1]){if(line=='fgf2'){line<-'FGF2'}}
> #I made sure that it was looping through each line by entering:
> for(line in dat[,1]){if(line=='fgf2'){print(line)}} #Which did
exactly
> what I thought it would.
>
> #This doesn't change anything, though.  Also, after reading the
> documentation I am still confused how to add multiple "if"
> statements.  I would need that because I need to change the names of
> fgf2, fgf7, and fgf10.
>
> #I am sure there is a built-in function to do what I need, but I
> haven't found it yet so I tried this loop method.  Any help is greatly
> appreciated!
>
> Jahan
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Phil Spector wrote:
> Jahan -
>    Try
> 
> dat$target = toupper(dat$target)

Note that in this case, the above *will* coerce dat$target
to a character vector, which may or may not be what
is intended.