R help - Mar 2007 - subset by multiple columns satisfying the same condition

Hi All,

I have a very simple question. Suppose I had a data frame with 100 columns,
now I wanted to select rows with the values of  some columns satisfying the
same condition, like all equal to "Tom". I know I can use the
'and' operator
"&", but it's painful if there were many columns.

Can anyone give me some advice? Thanks in advance,

FD

	[[alternative HTML version deleted]]

say x is you rdata frame and y is the vector of column indices you  
want to match to a condition:

x[apply(x[y]=="Tom",1,all),]

still, i feel like there's probably a better way...

On Mar 18, 2007, at 1:36 PM, Frank Duan wrote:
> Hi All,
>
> I have a very simple question. Suppose I had a data frame with 100  
> columns,
> now I wanted to select rows with the values of  some columns  
> satisfying the
> same condition, like all equal to "Tom". I know I can use the
'and'
> operator
> "&", but it's painful if there were many columns.
>
> Can anyone give me some advice? Thanks in advance,
>
> FD
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting- 
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

Frank Duan wrote:
> Hi All,
>
> I have a very simple question. Suppose I had a data frame with 100 columns,
> now I wanted to select rows with the values of  some columns satisfying the
> same condition, like all equal to "Tom". I know I can use the
'and' operator
> "&", but it's painful if there were many columns.
>
> Can anyone give me some advice? Thanks in advance,
>   
Here's one way:
 
rowSums(myframe != "Tom") == 0

The following approach might generalize more easily, though

 do.call("pmin", lapply(myframe, "==", "Tom"))

(notice that pmin on logical vectors is TRUE, if all are TRUE, else 
FALSE or NA).