R: How to split list into several numbers and do the calculation?

Question

my data is like: -3+2 41-12 after separating each part by using the following code: eg.

text = \'-3+2\'

pattern = \'-?\\\\d+\'
matches = gre         


        

Answer 1

I know it's bad form in general, but I think the simplest approach is to use eval and parse in these cases and completely skip the regex:

text = c("-3+2", "99+44-100")
sapply(text, function(x) eval(parse(text=x)))
#      -3+2 99+44-100 
#        -1        43 

If you dislike the names on the vectors you can instead do:

unname(sapply(text, function(x) eval(parse(text=x))))
# [1] -1 43

Answer 2

in your particular case (2 numbers):

as.integer(a[[1]][1]) + as.integer([[1]][2])

More generally:

sum(sapply(a[[1]], as.integer))

Answer 3

or from your list, after parsing:

sapply(a, function(x) sum(as.numeric(x)))