R help - Feb 2015 - grepping out columns

Hi,

I've got a complicated grep problem (or not)...  I currently have a
file with the headings as follows:

DAY
MONTH
YEAR
SA_TUES
SA_MON
SU_WED
CH_TUES
CH_WED
CH_MON
AR_TUES
AR_WED
AR_MON
SA_THUR
SU_FRI
CH_THUR
CH_FRI
AR_THUR
AR_FRI

I want to grep out all columns that have SA at the beginning of their
day including any other information pertaining to that day.
Ultimately I want to end up with:

SA_TUES
SA_MON
CH_TUES
CH_MON
AR_TUES
AR_MON
SA_THUR
CH_THUR
AR_THUR

Is there a way of doing this simply with grep? Or will this need to be
more complicated?

Thanks!

K.

On Feb 18, 2015, at 12:27 PM, Kate Ignatius wrote:
> Hi,
> 
> I've got a complicated grep problem (or not)...  I currently have a
> file with the headings as follows:
> 
Lets assume these values are in a character vector named
'dat'.
> SA_TUES
> SA_MON
> SU_WED
> CH_TUES
> CH_WED
> CH_MON
> AR_TUES
> AR_WED
> AR_MON
> SA_THUR
> SU_FRI
> CH_THUR
> CH_FRI
> AR_THUR
> AR_FRI
 sadays <- dat[grep("SA", dat) ]
 sads <- gsub("SA_","",sadays)
 sads
#[1] "TUES" "MON"  "THUR"

 dat[ sapply(sads, grep, dat) ]
#[1] "SA_TUES" "CH_TUES" "AR_TUES"
"SA_MON"  "CH_MON"  "AR_MON"
#[7] "SA_THUR" "CH_THUR" "AR_THUR

-- 
David Winsemius
Alameda, CA, USA

David's almost works except it catches the "MONTH" column, just
add an
empty metacharacter tho.

c("DAY",
"MONTH",
"YEAR",
"SA_TUES",
"SA_MON",
"SU_WED",
"CH_TUES",
"CH_WED",
"CH_MON",
"AR_TUES",
"AR_WED",
"AR_MON",
"SA_THUR",
"SU_FRI",
"CH_THUR",
"CH_FRI",
"AR_THUR",
"AR_FRI")-> columns

sa_ind <- grep("SA_",columns)
days <- gsub("SA_","", columns[sa_ind])
days <- paste0(days,"$")
selected <- lapply(days, function(x) grep(x,columns))
selected <- sort(unique(unlist(all_ind)))

columns[selected]
[1] "SA_TUES" "SA_MON"  "CH_TUES"
"CH_MON"  "AR_TUES" "AR_MON"
"SA_THUR" "CH_THUR" "AR_THUR"

On Wed, Feb 18, 2015 at 2:55 PM, David Winsemius <dwinsemius at
comcast.net> wrote:
>
> On Feb 18, 2015, at 12:27 PM, Kate Ignatius wrote:
>> Hi,
>>
>> I've got a complicated grep problem (or not)...  I currently have a
>> file with the headings as follows:
>>
> Lets assume these values are in a character vector named 'dat'.
>> SA_TUES
>> SA_MON
>> SU_WED
>> CH_TUES
>> CH_WED
>> CH_MON
>> AR_TUES
>> AR_WED
>> AR_MON
>> SA_THUR
>> SU_FRI
>> CH_THUR
>> CH_FRI
>> AR_THUR
>> AR_FRI
>
>  sadays <- dat[grep("SA", dat) ]
>  sads <- gsub("SA_","",sadays)
>  sads
> #[1] "TUES" "MON"  "THUR"
>
>  dat[ sapply(sads, grep, dat) ]
> #[1] "SA_TUES" "CH_TUES" "AR_TUES"
"SA_MON"  "CH_MON"  "AR_MON"
> #[7] "SA_THUR" "CH_THUR" "AR_THUR
>
> --
> David Winsemius
> Alameda, CA, USA
>
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