CODEWITHSUNDEEP
rdataframesum
fina
fina

Reputation: 451

Sum of values in a numeric column that are in the interval between two characters of another column (R)

Having this data frame:

   lt  vl
1   a 1.0
2     2.0
3     0.5
4     6.0
5     7.0
6   a 6.0
7     8.0
8     7.0
9     9.0
10  d 7.0
11     NA
12    0.5
13    8.0
14    5.0
15  g 6.0
16    7.0


lt<-c("a","","","","","a","","","","d","","","","","g","")

vl<-c(1,2,0.5,6,7,6,8,7,9,7,NA,0.5,8,5,6,7)

I want to sum each value in vl between characters of lt. The process has to be like this:

a=1+2+0.5+6+7
a=6+8+7+9
d=7+0.5+8+5
g=6+7

To finally obtain:

lt  vl
a   16.5
a   30
d   20.5
g   13

Note: a is different of a

I'm trying hard to solve this, but it is rather difficult for me.

Upvotes: 2

Views: 35

Answers (1)

Rui Barradas
Rui Barradas

Reputation: 76402

You can do this with tapply. The grouping factor is established with a standard cumsum trick.

f <- cumsum(lt != "")
res <- tapply(vl, f, FUN = sum, na.rm = TRUE)
names(res) <- lt[lt != ""]
res
#   a    a    d    g 
#16.5 30.0 20.5 13.0

Upvotes: 2

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