substitute a value according to specific condition in R

Question

i have a df structured like this:

 Value.  Numb. 
   46.   200
   47.   200
   55.   200
   21.   200
   32.   140
   23.   140
   56.   700

If numb value is repeated, I want to substitute the value with the result of the division Numb/number of times it appears, obtaining a new df:

 Value.  Numb. 
   46.    50
   47.    50
   55.    50
   21.    50
   32.    70
   23.    70
   56.   700

How can I do? better a solution comprising the use of dplyr.

number of times it appears overall in `Numb` column or consecutive number of times it appear ? — Ronak Shah, Feb 05 '19 at 10:15

score 2 · Answer 1 · answered Feb 05 '19 at 10:16

2

library(dplyr)
df %>% group_by(Numb.) %>% mutate(Number=Numb./n()) %>% ungroup()

answered Feb 05 '19 at 10:16

A. Suliman

score 1 · Answer 2 · answered Feb 05 '19 at 10:18

1

One way using ave is to create a grouping variable Numb and calculate the length of each group and divide the Numb by the length.

with(df, Numb/ave(Numb, Numb, FUN = length))
#[1]  50  50  50  50  70  70 700

answered Feb 05 '19 at 10:18

Ronak Shah

score 1 · Answer 3 · answered Feb 05 '19 at 11:01

1

One option is data.table. Grouped by 'Numb.', divide the column by the number of rows

library(data.table)
setDT(df)[, Numb. := Numb./.N, Numb.]

answered Feb 05 '19 at 11:01

akrun

3 Answers3