[R] Finding the position of a variable in a data.frame
ccleland at optonline.net
Wed Aug 2 23:12:53 CEST 2006
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
> 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))
> subset(Df, bat >= 50)
> 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
Why not do it this way?
Df$bat <- replace(Df$bat, Df$bat >=50, 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.
> R-help at stat.math.ethz.ch mailing list
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
Chuck Cleland, Ph.D.
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