Question

I am new to R and am getting unexpected results while using the ifelse() function. Here is an example. Below is a subset of the data frame I am working with. After the last command, why does the example$Points column contain 12 instead of 2? I have tried this for many different values of example$Value and the result is always 10 more than what I expect.

Example:

example
     Question StudentID SchoolID Value Worth Answer Points
2926       18    101290    84386     2     2     Co      0
2927       18    100878    84386     2     2     Co      0
2928       18    100895    84386     1     5     Co      0
2929       18    100913    84386     2     2     Co      0
2930       18    100884    84386     2     2     Co      0
example$Points <- ifelse(example$Answer == "Co", example$Value, example$Points)
example
     Question StudentID SchoolID Value Worth Answer Points
2926       18    101290    84386     2     2     Co     12
2927       18    100878    84386     2     2     Co     12
2928       18    100895    84386     1     5     Co     11
2929       18    100913    84386     2     2     Co     12
2930       18    100884    84386     2     2     Co     12

I’ve been using the work-around of just then subtracting 10 from the column, but I would like to avoid this and get to the bottom of what is going on here.

Any help would be greatly appreciated. Thank you!

Answer 1

My guess is that example$Value is a factor and you’re getting the underlying codes instead of the labels. I recommend taking a look at your data as soon as it’s read into R to see what’s causing your input method to treat those values as factors instead of integer / numeric.