[R] Confounded data frame column names

[Uwe Ligges]

Booker, Andrew J wrote:

> This is probably a know problem (problem for me anyway) in R but I
> don't quite know what to search for in help archives. When I name a
> column "x11" in a data frame R thinks a column named "x1" exists. 

Not exactly. R uses partial matching here. Iff "x11" and "x1" exists, 
"x11" will be selected. Pretty much like matching for arguments in 
functions.

Probably you are looking for names(temd)?

Uwe Ligges


 > In
> my application I am trying to test for the existence of a column, then
> add it if it's not there. Here is a simple example:
> 
> 
>>temd <- data.frame(x11=c(0:10))
>>is.null(temd[["x1"]])
> 
> [1] FALSE
> 
>>temd[["x1"]]
> 
>  [1]  0  1  2  3  4  5  6  7  8  9 10
> 
>>temd$x1
> 
>  [1]  0  1  2  3  4  5  6  7  8  9 10
> 
>>temd[,"x1"]
> 
> Error in "[.data.frame"(temd, , "x1") : undefined columns selected
> 
> 
> This is in R 2.0.0.
> 
> Anyone know how to run (safely) through a list of names like "x1"-"x100" and check for data frame columns with the names?
> 
> 
> 
> ----------------------------------------------------------- 
> * Opinions herein are mine only *
> ----------------------------------------------------------- 
> 
> 			Andrew Booker 	
> 			The Boeing Company
> 			P.O. Box 3707 MC 7L-22
> 			Seattle, WA  98124-2207
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> 			FAX# 425-865-2966
> 			andrew.j.booker at boeing.com
> 
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