CODEWITHSUNDEEP
rvectorsum
Arnaud Panes
Arnaud Panes

Reputation: 61

Sum number in a character string (R)

I have a vector that looks like :

numbers <- c("1/1/1", "1/0/2", "1/1/1/1", "2/0/1/1", "1/2/1")

(not always the same number of "/" character)

How can I create another vector with the sum of the numbers of each string?

Something like :

sum
3
3
4
4
4

Upvotes: 6

Views: 4707

Answers (3)

G. Grothendieck
G. Grothendieck

Reputation: 269654

1) strapply strapply matches each string of digits using \\d+ and then applies as.numeric to it returning a list with one vector of numbers per input string. We then apply sum to each of those vectors. This solution seems particularly short.

library(gsubfn)

sapply(strapply(numbers, "\\d+", as.numeric), sum)
## [1] 3 3 4 4 4

2) read.table This applies sum(read.table(...)) to each string. It is a bit longer (but still only one line of code) but uses no packages.

sapply(numbers, function(x) sum(read.table(text = x, sep = "/")))
##   1/1/1   1/0/2 1/1/1/1 2/0/1/1   1/2/1 
##       3       3       4       4       4

Add the USE.NAMES = FALSE argument to sapply if you don't want names on the output.

scan(textConnection(x), sep = "/", quiet = TRUE) could be used in place of read.table but is longer.

Upvotes: 0

Tim Biegeleisen
Tim Biegeleisen

Reputation: 521289

What seems to me to be the most straightforward approach here is to convert your number strings to actual valid string arithmetic expressions, and then evaluate them in R using eval along with parse. Hence, the string 1/0/2 would become 1+0+2, and then we can simply evaluate that expression.

sapply(numbers, function(x) { eval(parse(text=gsub("/", "+", x))) })

1/1/1   1/0/2 1/1/1/1 2/0/1/1   1/2/1 
    3       3       4       4       4

Demo

Upvotes: 3

LyzandeR
LyzandeR

Reputation: 37879

One solution with strsplit and sapply:

sapply(strsplit(numbers, '/'), function(x) sum(as.numeric(x)))
#[1] 3 3 4 4 4

strsplit will split your stings on / (doesn't matter how many /s you have). The output of strsplit is a list, so we iterate over it to calculate the sum with sapply.

Upvotes: 5

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