I am trying to figure it out how I can use tstrisplit() function from data.table to split a text by location number. I am aware of the Q1, Q2 & Q3 but these do not address my question.
as an example :
DT2 <- data.table(a = paste0(LETTERS[1:5],seq(10,15)), b = runif(6))
DT2
a b
1: A10 0.4153622
2: B11 0.1567381
3: C12 0.5361883
4: D13 0.5920144
5: E14 0.3376648
6: A15 0.5503773
I tried the following which did not work:
DT2[, c("L", "D") := tstrsplit(a, "")][]
DT2[, c("L", "D") := tstrsplit(a, "[A-Z]")][]
DT2[, c("L", "D") := tstrsplit(a, "[0-9]{1}")][]
The expectation:
a b L D
1: A10 0.4153622 A 10
2: B11 0.1567381 B 11
3: C12 0.5361883 C 12
4: D13 0.5920144 D 13
5: E14 0.3376648 E 14
6: A15 0.5503773 A 15
any help with explanation is highly appreciated.
You can split on regex "(?<=[A-Za-z])(?=[0-9])" if you want to split between letters and digits, (?<=[A-Za-z])(?=[0-9]) restricts the split to a position that is preceded by a letter and followed by a digit:
The regex contains two parts, look behind (?<=[A-Za-z]) which means after a letter and look ahead (?=[0-9]), i.e before a digit, see more about regex look around, in r, you need to specify perl=TRUE to use Perl-compatible regexps to make these work:
DT2[, c("L", "D") := tstrsplit(a, "(?<=[A-Za-z])(?=[0-9])", perl=TRUE)][]
# a b L D
#1: A10 0.01487372 A 10
#2: B11 0.95035709 B 11
#3: C12 0.49230300 C 12
#4: D13 0.67183871 D 13
#5: E14 0.40076579 E 14
#6: A15 0.27871477 A 15