Cumulative sum for more values in one entry-CodePudding

Let's say I have this dataframe (the "number" variable is also from character-type in the original dataframe):

df <- data.frame(
  id = c(1,2,2,1,2),
  number = c(30.6, "50.2/15.5", "45/58.4", 80, "57/6"))
df$number <- as.character(df$number)

Now I want to add another column with the cumulative sum for each ID and I did this with df %>% mutate(csum = ave(number, id, FUN=cumsum)), which works for the single numbers, but of course not for the numbers separated with "/". How can I solve this problem?

The final dataframe should be like this:

df2 <- data.frame(
  id = c(1,2,2,1,2),
  number = c(30.6, "50.2/15.5", "45/58.4", 80, "57/6"),
  csum = c(30.6, "50.2/15.5", "95.2/73.9", 110.6, "152.2/79.9"))
df2

CodePudding user response：

One way could be:

group with group_by
separate in column a and b
mutate across a and b and apply cumsum
unite from tidyr package using na.rm=TRUE argument

library(dplyr)
library(tidyr)

df %>% 
  group_by(id) %>% 
  separate(number, c("a", "b"), sep="/", remove = FALSE, convert = TRUE) %>% 
  mutate(across(c(a,b), ~cumsum(.))) %>% 
  unite(csum, c(a,b), sep = '/', na.rm = TRUE)

     id number    csum      
  <dbl> <chr>     <chr>     
1     1 30.6      30.6      
2     2 50.2/15.5 50.2/15.5 
3     2 45/58.4   95.2/73.9 
4     1 80        110.6     
5     2 57/6      152.2/79.9

CodePudding user response：

You could use the extremely fast matrixStats::colCumsums.

res <- do.call(rbind, by(df, df$id, \(x) {
  cs <- matrixStats::colCumsums(do.call(rbind, strsplit(x$number, '/')) |> 
                                  type.convert(as.is=TRUE))
  r <- do.call(paste, c(as.list(as.data.frame(cs)), sep='/'))
  data.frame(id=x$id, number=x$number, csum=r)
}))

Note: R version 4.1.2 (2021-11-01).

Gives:

res
#     id    number       csum
# 1.1  1      30.6       30.6
# 1.2  1        80      110.6
# 2.1  2 50.2/15.5  50.2/15.5
# 2.2  2   45/58.4  95.2/73.9
# 2.3  2      57/6 152.2/79.9