Comparing Values in Individual Rows to Corresponding Rows In Different Column

Question

I'm new to the forum and relatively new to R.

I'm currently manipulating my data. The data are placed in a DataFrame. I'd like to compare the values in each row of column 'Prime' to each corresponding row of column 'target'. If the values match I want to add the value '1' to the corresponding row in column 'Match' and if they don't match add a '0'.

Below is an example of the columns and the solution under column 'Match'

Prime    Target  Match
faces0   faces0   1 
faces0   faces0   1 
houses1  faces0   0

I toyed around using ifelse and identical but it compares the objects as a whole and not the individual and corresponding rows.

Can anyone suggest a means of comparing Prime and Target while assigning a value to Match dependant on a match being made or not?

Thanks very much for your time.

Answer 1

This is a straight logical test, so if you compare the two columns for equality, you will get TRUE/FALSE, which can easily be converted to 1/0 with as.numeric(). Depending on how your columns are coded, they may need to be converted to character before the comparison:

dat$Match <- as.numeric(dat$Prime == dat$Target)
dat$Match
# [1] 1 1 0

Answer 2

You can use ifelse or matchbut need to convert to numeric before that. Here is the solution.

mydata<-structure(list(Prime = structure(c(1L, 1L, 2L), .Label = c("faces0", 
"houses1"), class = "factor"), Target = structure(c(1L, 1L, 1L
), .Label = "faces0", class = "factor"), Match = c(1, 1, 0)), .Names = c("Prime", 
"Target", "Match"), row.names = c(NA, -3L), class = "data.frame")

> mydata$Match<-with(mydata,ifelse(as.numeric(Prime)==as.numeric(Target),1,0))
> mydata
    Prime Target Match
1  faces0 faces0     1
2  faces0 faces0     1
3 houses1 faces0     0

mydata$Match<-with(mydata,match(as.numeric(Prime),as.numeric(Target),nomatch=0))
 > mydata
        Prime Target Match
    1  faces0 faces0     1
    2  faces0 faces0     1
    3 houses1 faces0     0