How to create new variables using loop and ifelse statement

Question

I have a number of variables with the same name but different suffixes. For example, var1, var2, var3, var4, var5, var6, ... and so on. Each of these variables has a random sequence of 0, 1, and 2. Using these variables, I am trying to create a new variable called testvariable. If any of the already existing variables has 1, I will set testvariable to 1. If they have 0 or 2, I will assign 0.

Is there a simple loop and/or ifelse statement I can use to create this variable? My real data is a lot more complex than this, so I don't want to copy and paste each individual variable and values.

Edit: This is for R.

Answer 1

If I understand you correctly, if any of the variables like var1, var2, .., etc has a value 1, then the testvariable must be 1 else 0, then do:

Sample df:

  var1 var2 var3 var4 var5
1    1    1    1    1    1
2    2    2    2    2    2
3    0    1    0    1    0
4    0    0    0    0    1
5    1    1    2    1    2
6    2    2    2    2    2
7    2    2    1    2    2
8    1    1    2    1    1
9    0    0    0    0    0

Code:

df$testvariable <- ifelse(rowSums(df[, grepl("var", names(df))] == 1) > 0, 1, 0)

Output:

  var1 var2 var3 var4 var5 testvariable
1    1    1    1    1    1            1
2    2    2    2    2    2            0
3    0    1    0    1    0            1
4    0    0    0    0    1            1
5    1    1    2    1    2            1
6    2    2    2    2    2            0
7    2    2    1    2    2            1
8    1    1    2    1    1            1
9    0    0    0    0    0            0

Answer 2

I would use mget for this. mget gives the variables as a list. Then you can check for each element of the list using sapply and combine the results using any. At the end I took advantage of your encoding of 0 and 1, but you can also use an if statement.

var1 <- c(0,0,1,2)
var2 <- c(2,2,2,2)
var3 <- c(0,2,0,2)
var4 <- c(0,2,2,2)

any(sapply(mget(paste0("var", 1:4)), function(x) 1 %in% x)) * 1
#> [1] 1

any(sapply(mget(paste0("var", 2:4)), function(x) 1 %in% x)) * 1
#> [1] 0