R help - Oct 2003 - Searching a Table

Is there any way to search a column of a table?

 

I read in a table and I want to create a subset based on the criteria that a
certain column (filled with words) has a word which starts with a certain
letter. The only method I have seen that searches this way is apropos(), but
that doesn't seem to search the location I want. If anyone can make a
recommendation I would appreciate it.

 

Thanks!

Nicole Baggette


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Nicole Baggette wrote:
> Is there any way to search a column of a table?
> 
>  
> 
> I read in a table and I want to create a subset based on the criteria that
a
> certain column (filled with words) has a word which starts with a certain
> letter. The only method I have seen that searches this way is apropos(),
but
> that doesn't seem to search the location I want. If anyone can make a
> recommendation I would appreciate it.
help(grep)

To search for words that start with "W" or "w" (minus the
quotes) in a
data frame called "mydata", column 3,

grep("\\bw", mydata[,3], ignore.case=TRUE, perl=TRUE)

Which means - "\\b" - word boundary.
The "w" and ignore.case should be self-explanatory.
perl - use perl style regular expressions.

example:

foo <- c("now is The Time","for all good llamas","to
come to the party")
foo

#find lines that contain words starting with "t" or "T"

grep("\\bt",foo,ignore.case=TRUE,perl=TRUE)

foo[grep("\\bt",foo,ignore.case=TRUE,perl=TRUE)]

Cheers

Jason
-- 
Indigo Industrial Controls Ltd.
http://www.indigoindustrial.co.nz
64-21-343-545
jasont at indigoindustrial.co.nz