[R] selecting columns based on values of two variables

[Dimitris Rizopoulos]

probably you're looking for

subset(capdist, ida %in% c("DEN","SWD","FIN") & idb %in% 
c("DEN","SWD","FIN"))


I hope it helps.

Best,
Dimitris


Thomas Jensen wrote:
> Dear R-list,
> 
> I am having troubles selecting rows from a very large data-set  
> containing distances between capitals.
> 
> The structure of the data-set looks like this:
> 
>       	numa 	ida 		numb 	idb 		kmdist 	midist
> 1        2 		USA   	20 		CAN    	731    	456
> 2        2	 	USA   	31 		BHM   	1623   	1012
> 3        2 		USA   	40 		CUB   	1813   	1130
> 
> 
> I want to select a subset of these dyads, and have tried the following  
> code:
> 
> subset(capdist,ida == c("DEN","SWD","FIN") & idb ==  
> c("DEN","SWD","FIN"))
> 
> This should ideally give me the dyads involving only Denmark, Sweden  
> and Finland, however i get the error message:
> 
> [1] numa   ida    numb   idb    kmdist midist
> <0 rows> (or 0-length row.names)
> Warning messages:
> 1: In is.na(e1) | is.na(e2) :
>    longer object length is not a multiple of shorter object length
> 2: In `==.default`(ida, c("DEN", "SWD", "FIN")) :
>    longer object length is not a multiple of shorter object length
> 3: In is.na(e1) | is.na(e2) :
>    longer object length is not a multiple of shorter object length
> 4: In `==.default`(idb, c("DEN", "SWD", "FIN")) :
>    longer object length is not a multiple of shorter object length
> 
> Any help would be greatly appreciated,
> 
> Best, Thomas Jensen
> 	[[alternative HTML version deleted]]
> 
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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