R help - May 2015 - Grep out columns using a list of strings

Hi,

I have a list of 150 strings, say, ap,:

aajkss
dfghjk
sdfghk
...
xxcvvn


And I would l like to grep out these strings from column names in
another file, af,.   I've tried the following but none seem to work:

aps <- af[,grep(ap, colnames(af), value=TRUE)]
aps <- af[,grep(ap, colnames(af), value=FIXED)]
aps <- af[,grep(as.character(list(ap),colnames(af))]

and also aps <- unique (grep(ap, colnames(af))

Is there another way I can do this - maybe without using grep?

Thanks!

Kate.

How about %in% ?


# preparing something that looks like I think your data looks like:
ap <- c("aajkss", "dfghjk", "sdfghk",
"xxcvvn")
af <- matrix(1:10, nrow=2)
colnames(af) <- c("aajkss", "b", "c",
"dfghjk", "e")

# doing what I think you need done:
ap[ap %in% colnames(af)]


Cheers,
B.

(PS. a reproducible example saves us all time and unnecessary effort. :-)





On May 8, 2015, at 3:50 PM, Kate Ignatius <kate.ignatius at gmail.com>
wrote:
> Hi,
> 
> I have a list of 150 strings, say, ap,:
> 
> aajkss
> dfghjk
> sdfghk
> ...
> xxcvvn
> 
> 
> And I would l like to grep out these strings from column names in
> another file, af,.   I've tried the following but none seem to work:
> 
> aps <- af[,grep(ap, colnames(af), value=TRUE)]
> aps <- af[,grep(ap, colnames(af), value=FIXED)]
> aps <- af[,grep(as.character(list(ap),colnames(af))]
> 
> and also aps <- unique (grep(ap, colnames(af))
> 
> Is there another way I can do this - maybe without using grep?
> 
> Thanks!
> 
> Kate.
> 
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