CODEWITHSUNDEEP
r
mlinegar
mlinegar

Reputation: 1399

Grep a 1 or 2 character number from a variable in R

I have two tables, Grow and Temp. Grow details the growing and nongrowing seasons for each area I'm concerned with (these are static), while Temp details the average temperature each month of a wide range of years (these are columns) for those same areas. I'm trying to identify the average temperature each year for the growing and nongrowing seasons, but I've run into a problem with how I pick the columns - I'm using grep, but can't figure out how to account for two-digit months!

At this point I've isolated each column of years, and have a vector of column names for a single year - something like "tmp_2001_1" "tmp_2001_2" "tmp_2001_3" ... "tmp_2001_11" "tmp_2001_12". I also have, stored in a pair of variables, the start and end of growing season, which are stored as integers representing months: start <- some number between 1 and 12, end <- some number between 1 and 12. But I can't figure out how to get grep to identify the growing season when start or end has 2 digits. This is what I have that works for the case of them both being 1 digit numbers:

grow_months <- grep(paste('tmp_','2001','_','[',start,'-',end,']',sep = ''), vector_of_column_names)

How can I expand this to account for cases where start or end is double digit?

Upvotes: 0

Views: 134

Answers (1)

snacks
snacks

Reputation: 454

As Gregor suggests,

strings = paste0("tmp_2001_",c(1:20,100))
start = 9
end = 12
ii = sapply(strsplit(strings,'_'), function(x)x[3]%in%start:end)
strings[ii]

or using an easy regex you could try

ii = grep(paste(paste0('_(',start:end,')$'),collapse='|'), strings)
strings[ii]

Upvotes: 1

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