[R] Finding the position of a variable in a data.frame

[John Kane]

--- roger koenker <rkoenker at uiuc.edu> wrote:

> it is the well-known wicked which problem:  if you
> had (grammatically  
> incorrectly)
> thought "... which I want to change" then you might
> have been led
> to type (in another window):
> 
> 	?which
> 
> and you would have seen the light.  Maybe that()
> should be an alias
> for which()?

One also has to understand which and I missed it.  I
don't think that which is really that grammatically
incorrect anymore.

Thanks
> 
> url:    www.econ.uiuc.edu/~roger            Roger
> Koenker
> email    rkoenker at uiuc.edu            Department of
> Economics
> vox:     217-333-4558                University of
> Illinois
> fax:       217-244-6678                Champaign, IL
> 61820
> 
> 
> On Aug 2, 2006, at 4:01 PM, John Kane wrote:
> 
> > Simple problem but I don't see the answer. I'm
> trying
> > to clean up some data
> > I have 120 columns in a data.frame.  I have one
> value
> > in a column named "blaw" that I want to change.
> How do
> > I find the coordinates. I can find the row by
> doing a
> > subset on the data.frame but how do I find out
> here
> > "blaw " is in columns without manually counting
> them
> > or converting names(Df) to a list and reading down
> the
> > list.
> >
> > Simple example
> >
> > cat <- c( 3,5,6,8,0)
> > dog <- c(3,5,3,6, 0)
> > rat <- c (5, 5, 4, 9, 0)
> > bat <- c( 12, 42, 45, 32, 54)
> >
> > Df <- data.frame(cbind(cat, dog, rat, bat))
> > Df
> > subset(Df, bat >= 50)
> >
> > ----results
> >   cat dog rat bat
> > 5   0   0   0  54
> >
> >
> > Thus I know that my target is in row 5 but how do
> I
> > figure out where 'bat' is?
> >
> > All I want to do is be able to say
> > Df[5,4] <- 100
> >
> > Is there some way to have function(bat) return the
> > column number: some kind of a colnum() function? 
> I
> > had thought that I had found somthing  in
> > library(gdata) matchcols but no luck.
> >
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> 
>