[R] Searching for specific values in a matrix

[Steve Lianoglou]

On Jul 21, 2009, at 1:47 PM, Mehdi Khan wrote:

> Hello all,
>
> I have a seemingly simple question which I have searched for an  
> answer for
> for a few hours without luck.  I have a matrix of both values and  
> characters
> with thousands of rows.  I would like to run a search of this matrix  
> for
> certain values and would like the search to retrieve the entire  
> row.  How
> would I accomplish this?

Oh, values! Woops

Like so?

df <- data.frame(nums=1:10, words=c("Abelonian",
     "abeltree",
     "Abencerrages",
     "abenteric",
     "abepithymia",
     "Aberdeen",
     "aberdevine",
     "Aberdonian",
     "Aberia",
     "aberrance"))

evens <- df$nums %% 2 == 0
df[evens,]

You can build such an indexing vector (like evens) in a number of  
different ways to suite your problem.

-steve

--
Steve Lianoglou
Graduate Student: Physiology, Biophysics and Systems Biology
Weill Medical College of Cornell University

Contact Info: http://cbio.mskcc.org/~lianos/contact