How to create new var by row with random choice?

user_12933738 0
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With dplyr, I would like to create a new variable new_regsiege with the following conditions:

For each line and "XX" if regsiege=="XX" and nbeta_regXX>0 then new_regsiege=regsiege

if regsiege=="XX" and nbeta_regXX=0 then new_regsiege is one of the regsiege randomly chosen among those which are not null.

Here's my example :

mydf <- data.frame(
  regsiege = c("11","24","93"),
  nbeta_reg11 = c(0,1,0),
  nbeta_reg24 = c(1,1,0),
  nbeta_reg93 = c(1,1,1)
)

# Desired output
regsiege nbeta_reg11 nbeta_reg24 nbeta_reg93 new_regsiege
      11           0           1           1           93 (could be also "24")
      24           1           1           1           24
      93           0           0           1           93

I started like this :

mydf %>% 
  rowwise()
  mutate(
    new_regsiege = if_else(...
  )
dplyr dataframe r
2 Answers

You could try

library(tidyverse)

mydf %>%
  pivot_longer(-1, names_prefix = "nbeta_reg") %>%
  group_by(regsiege) %>%
  summarise(new_regsiege = if(value[regsiege == name] > 0) regsiege[1]
                           else sample(name[value > 0], 1)) %>%
  left_join(mydf, ., by = "regsiege")

#   regsiege nbeta_reg11 nbeta_reg24 nbeta_reg93 new_regsiege
# 1       11           0           1           1           93
# 2       24           1           1           1           24
# 3       93           0           0           1           93
user_100689850

The simplest solution would use a loop:

for (i in seq_len(nrow(mydf))) {
  cur_regsiege  <- mydf[i, "regsiege"]
  same          <- mydf[i, paste0("nbeta_reg", cur_regsiege)]
  mydf[i, "new_regsiege"] <- if (same) cur_regsiege else sample(mydf[-i, "regsiege"], 1L)
}

#   regsiege nbeta_reg11 nbeta_reg24 nbeta_reg93 new_regsiege
# 1       11           0           1           1           93
# 2       24           1           1           1           24
# 3       93           0           0           1           93
user_45522950
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