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Sorry for a very basic question, solution must be very simple but I'm not able to find it.
Trying to use gsub adding a new column in a data.table, I got the warning "argument 'replacement' has length > 1 and only the first element will be used", and all data.table rows have, in the new column, the value of the first row.
Here is a semplified case:
dt <- data.table(v1=c(1,2,3) , v2=c("axb","cxxd","exfxgx"))
dt[ , v3:=gsub("x",v1,v2)]
The new column v3 contains a string with "1" instead of "x" in all the rows.
Using other functions, e.g.
dt[ , v3:=paste(v1,v2)]
works as expected.
I'm using Rstudio v.0.98.1103 , R v.3.1.2, data.table v.1.9.4
830
To remove a character in an R data frame column, we can use gsub function which will replace the character with blank. For example, if we have a data frame called df that contains a character column say x which has a character ID in each value then it can be removed by using the command gsub("ID","",as.
The gsub() function in R is used to replace the strings with input strings or values. Note that, you can also use the regular expression with gsub() function to deal with numbers. This is data that has 'R' written multiple times.
Description Generalized "gsub" and associated functions. gsubfn is an R package used for string matching, substitution and parsing.
dt[, v3 := gsub("x", v1, v2), by = v1]
The easiest approach would be to use a string processing package that has vectorized arguments, like stringi:
library(stringi)
dt[, v3 := stri_replace_all_fixed(v2, "x", v1)][]
# v1 v2 v3
# 1: 1 axb a1b
# 2: 2 cxxd c22d
# 3: 3 exfxgx e3f3g3
Alternatively, you can make your own "vectorized" version of gsub by using the Vectorize function:
vGsub <- Vectorize(gsub, vectorize.args = c("replacement", "x"))
dt[, v3 := vGsub("x", v1, v2)][]
# v1 v2 v3
# 1: 1 axb a1b
# 2: 2 cxxd c22d
# 3: 3 exfxgx e3f3g3
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