[R] concise syntax for selecting multiple rows

[David Winsemius]

On Apr 26, 2010, at 11:12 AM, John Sorkin wrote:

> I would like to select rows if a row contains any one of several  
> values. I can do the selection as follows:
>
> result[,"Subject"]=="JEFF" | result[,"Subject"]=="BG"
>
> But this is very unwieldily if one wishes to select many, many rows  
> as one has to continuously repeat the source:
>
> result[,"Subject"]=="JEFF" | result[,"Subject"]=="BG" |  
> result[,"Subject"]=="John"  |  result[,"Subject"]=="Mary"
>
> Is there an easier way? I tried the following but it did not work:
>
>
> result[,"Subject"]==c("JEFF" | "BG" | "John"  | "Mary")

?%in%

To select rows the logical vector needs to be in the first position of  
[ , ]

result[result$Subject %in% =c("JEFF" , "BG" , "John" , "Mary") , ]

-- 
David.

>
> Thanks,
> John
>
>
>
> John David Sorkin M.D., Ph.D.
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
> (Phone) 410-605-7119
> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>
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David Winsemius, MD
West Hartford, CT