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

From: jim holtman <jholtman_at_gmail.com>
Date: Thu 03 Aug 2006 - 07:10:50 EST

?which

> which(Df >= 50, arr.ind=T)

  row col
5 5 4

On 8/2/06, John Kane <jrkrideau@yahoo.ca> 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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> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

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Received on Thu Aug 03 07:23:12 2006

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