Conditionally creating multiple variables

Question

I am trying to create multiple variables based on a condition using R dplyr. I have to write the same condition three times to get this work but I am guessing that there is an efficient way to do this task by writing the condition once and using that condition to create multiple variables. The reason I am trying to do this is, if there is a change in the condition, it will be easier to update the condition at one single location instead of updating it three times. Please help.

Example:

Current solution:

library(dplyr)

x = c(12,8,3)

df<-data.frame(x)

y<- df %>% mutate( a = ifelse(x>10 ,1,
                       ifelse(x>5  ,11,0)),

                   b = ifelse(x>10 ,2,
                       ifelse(x>5  ,12,0)),

                   c = ifelse(x>10 ,3,
                       ifelse(x>5  ,13,0))            
           )

Looking for something like this:

if      x>10 then
    {a=1 b=2 c=3}
else if x>5 then
    {a=11 b=12 c=13} 
else
    {a=0 b=0 c=0}

I'm actually not able to understand your actual purpose of efficient way. But one obvious optimization is to execute a=0 b=0 c=0 above if so that you can avoid last else part. — MKR
– MKR, Commented Jan 4, 2018 at 23:44

G. Grothendieck · Accepted Answer · 2018-01-05 00:04:23Z

3

Define a function and use it three times:

cond <- function(x, x1, x2) 
  case_when(
     x > 10 ~ x1,
     x >  5 ~ x2,
     TRUE ~ 0)

df %>% mutate(a = cond(x, 1, 11), b = cond(x, 2, 12), c = cond(x, 3, 13))

answered Jan 5, 2018 at 0:04

G. Grothendieck

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