Iteration over data.table

user_18148945 0
Viewed 64

I have a table A with column names: Var1, Var2, Var3.

Var1 = c("N1", "N2", "0", "0", "N3", "N4", "0", "0")
Var2 = c("0", "A", "0", "0", "0", "B", "0", "0")
Var3 = c("0", "Yes", "No", "All", "0", "x", "y", "z")

I would like to obtain vectors based on Table A, which contains values from column eg: N2 = (Yes, No, All), N4 = (x, y, z). I have tried few iterations with "for loop" and "logical if" but with no success. Please, give me some hint.

data.table dplyr tidyverse r
1 Answers

With data.table:

  • replace the 0s in Var1 by NA
  • carry forward last occurence of non NA values (using for example zoo::na.locf because data.table::nafill doesnt yet work for characters).
  • filter according to Var1:
library(data.table)
data <- data.table(Var1 = c("N1", "N2", "0", "0", "N3", "N4", "0", "0"), Var2 = c("0", "A", "0", "0", "0", "B", "0", "0"), Var3 = c("0", "Yes", "No", "All", "0", "x", "y", "z"))

# replace 0s by NA for next step
data[Var1==0,Var1:=NA]

# last occurence carried forward
data[,Var1:=zoo::na.locf(Var1)]

data[Var1=='N2',Var3]
#[1] "Yes" "No"  "All"

data[Var1=='N4',Var3]
#[1] "x" "y" "z"
user_135133280
Related