How to manipulate digits in a character string in R? - r

Question

I feel like I have a super easy question but for the life of me I can't find it when googling or searching here (or I don't know the correct terms to find a solution) so here goes.
I have a large amount of text in R in which I want to identify all numbers/digits, and add a specific number to them, for example 5.
So just as a small example, if this were my text:
text <- c("Hi. It is 6am. I want to leave at 7am")
I want the output to be:
> text
[1] "Hi. It is 11am. I want to leave at 12am"
But also I need the addition for each individual digit, so if this is the text:
text <- c("Hi. It is 2017. I am 35 years old.")
...I want the output to be:
> text
[1] "Hi. It is 75612. I am 810 years old."
I have tried 'grabbing' the numbers from the string and adding 5, but I don't know how to then get them back into the original string so I can get the full text back.
How should I go about this? Thanks in advance!

Answer 1

Here is how I would do the time. I would search for a number that is followed by am or pm and then sub in a math expression to be evaluated by gsubfn. This is pretty flexible, but would require whole hours in its current implementation. I added an am and pm if you wanted to swap those, but I didn't try to code in detecting if the number changes from am to pm. Also note that I didn't code in rolling from 12 to 1. If you add numbers over 12, you will get a number bigger than 12.
text1 <- c("Hi. It is 6am. I want to leave at 7am")
text2 <- c("It is 9am. I want to leave at 10am, but the cab comes at 11am. Can I push my flight to 12am?")
change_time <- function(text, hours, sign, am_pm){
string_change <- glue::glue("`(\\1{sign}{hours})`{am_pm}")
gsub("(\\d+)(?=am|pm)(am|pm)", string_change, text, perl = TRUE)|>
gsubfn::fn$c()
}
change_time(text = text1, hours = 5, sign = "+", am_pm = "am")
#> [1] "Hi. It is 11am. I want to leave at 12am"
change_time(text = text2, hours = 3, sign = "-", am_pm = "pm")
#> [1] "It is 6pm. I want to leave at 7pm, but the cab comes at 8pm. Can I push my flight to 9pm?"

Answer 2

text1 <- c("Hi. It is 2017. I am 35 years old.")
text2 <- c("Hi. It is 6am. I want to leave at 7am")
change_number <- function(text, change, sign){
string_change <- glue::glue("`(\\1{sign}{change})`")
gsub("(\\d)", string_change, text, perl = TRUE) %>%
gsubfn::fn$c() }
change_number(text = text1, change = 5, sign = "+")
#>[1] "Hi. It is 75612. I am 810 years old."
change_number(text = text2, change = 5, sign = "+")
#>[1] "Hi. It is 11am. I want to leave at 12am"
This works perfectly. Many thanks to #AndS., I tweaked (or rather, simplified) your code to fit my needs better. I was determined to figure out the other text myself haha, so thanks for showing me how!

Answer 3

Something quick and dirty with base R:
add_n = \(x, n, by_digit = FALSE) {
if (by_digit) ptrn = "[0-9]" else ptrn = "[0-9]+"
tmp = gregexpr(ptrn, x)
raw = regmatches(x, gregexpr(ptrn, x))
raw_plusn = lapply(raw, \(x) as.integer(x) + n)
for (i in seq_along(x)) regmatches(x[i], tmp[i]) = raw_plusn[i]
x
}
text = c(
"Hi. It is 6am. I want to leave at 7am",
"wow it's 505 dollars and 19 cents",
"Hi. It is 2017. I am 35 years old."
)
> add_n(text, 5)
# [1] "Hi. It is 11am. I want to leave at 12am"
# [2] "wow it's 510 dollars and 24 cents"
# [3] "Hi. It is 2022. I am 40 years old."
> add_n(text, -2)
# [1] "Hi. It is 4am. I want to leave at 5am" "wow it's 503 dollars and 17 cents"
# [3] "Hi. It is 2015. I am 33 years old."
> add_n(text, 5, by_digit = TRUE)
# [1] "Hi. It is 11am. I want to leave at 12am"
# [2] "wow it's 10510 dollars and 614 cents"
# [3] "Hi. It is 75612. I am 810 years old."

Answer 4

Here's a tidyverse solution:
data.frame(text) %>%
# separate `text` into individual characters:
separate_rows(text, sep = "(?<!^)(?!$)") %>%
# add `5` to any digit:
mutate(
# if you detect a digit...
text = ifelse(str_detect(text, "\\d"),
# ... extract it, convert it to numeric, add `5`:
as.numeric(str_extract(text, "\\d")) + 5,
# ... else leave `text` as is:
text)
) %>%
# string the characters back together:
summarise(text = str_c(text, collapse = ""))
# A tibble: 1 × 1
text
<chr>
1 Hi. It is 11am. I want to leave at 12am
Data 1:
text <- c("Hi. It is 6am. I want to leave at 7am")
Note that the same code works for the second text as well without any change:
# A tibble: 1 × 1
text
<chr>
1 Hi. It is 75612. I am 810 years old.
Data 2:
text <- c("Hi. It is 2017. I am 35 years old.")