Confusion of nested ifelse expression-CodePudding

Consider below expression:

x$Y = ifelse(x$A<= 5 & abs(x$B) >= 2, 
            ifelse(x$B> 2 ,"YES","NO"),
            'NA')

What I understand is that, if A is <=5 and B >=2 then ALL are YES, if not then NO, but I am confused the second ifelse condition. Any help will be highly appreciated.

Thanks

CodePudding user response：

If we rewrite your ifelse expression using expanded syntax, it might be easier to understand.

x$Y <- ifelse(x$A <= 5 & abs(x$B) >= 2, ifelse(x$B > 2, "YES", "NO"), 'NA')

# becomes

if (x$A <= 5 & abs(x$B) >= 2) {
    if (x$B > 2) {
        x$Y <- "YES"
    } else {
        x$Y <- "NO"
    }
} else {
    x$Y <- NA
}

The second nested ifelse() corresponds to the inner if above. It checks the value of x$B to see if it be greater than 2, or less than -2 (one of these much be the case based on the earlier check abs(x$B) >= 2. If the former be the case, then x$Y gets assigned to YES, otherwise it gets assigned to NO.

CodePudding user response：

This code aims to define a new column, Y in the data set x. The column Y will populate based on the following statements: