[R] Need help figuring out sapply (and similar functions) with multiple parameter user defined function

[Walter Anderson]

I am having trouble understanding how to use sapply (or similar 
functions) with a user defined function with multiple parameters.

I have the following functions defined

    q1.ans <- function(x)
    {
       retVal = 0
       if (x == 1) {
         retVal = 1
       } else if (x ==2) {
         retVal = 2
       }
       return (retVal)
    }
    q2.ans <- function(x)
    {
       retVal = 0
       if (x == 1) {
         retVal = 1
       } else if (x ==2) {
         retVal = 3
       }
       return (retVal)
    }
    q3.ans <- function(x)
    {
       retVal = 0
       if (x == 1) {
         retVal = 2
       } else if (x ==2) {
         retVal = 3
       }
       return (retVal)
    }

    evaluate.questions <- function(q.1,q.2,q.3)
    {
       a <- q1.ans(q.1)
       b <- q2.ans(q.2)
       c <- q3.ans(q.3)
       retVal = 0   # Set default value to be no preference
       # The following code only implements those values from the state
    machine that show a preference (ID's 5,9,11,13-15,17-18,21,23-27)
       if (a == 0) {
         if (b == 1) {
           if (c == 1) {
             retVal = 1  # State machine ID 5
           }
         } else if (b == 2) {
           if (c == 2) {
             retVal = 2  # State machine ID 9
           }
         }
       } else if (a == 1) {
         if (b == 0) {
           if (c == 1) {
             retVal = 1  # State machine ID 11
           }
         } else if (b == 1) {
           retVal = 1    # State machine ID's 13-15, value of C doesn't
    matter
         } else if (b == 2) {
           if (c == 1) {
             retVal = 1  # State machine ID 17
           } else if (c == 2) {
             retVal = 2  # State machine ID 18
           }
         }
       } else if (a == 2) {
         if (b == 0) {
           if (c == 2) {
             retVal = 2  # State machine ID 21
           }
         } else if (b == 1) {
           if (c == 1) {
             retVal = 1  # State machine ID 23
           } else if (c == 2) {
             retVal = 2  # State machine ID 24
           }
         } else if (b == 2) {
           retVal = 2    # State machine ID's 25-27, value of C doesn't
    matter
         }
       }
       return (retVal)
    }

And a data set that looks like this:

    ID,Q1,Q2,Q3
    1,2,2,2
    2,2,1,1
    3,1,1,1
    4,1,2,2
    5,2,2,1
    6,1,2,1
    ...


I have been researching and it appears that I should be using the sapply 
function to apply the evaluate.question function above to each row in 
the data frame like this

preferences <- sapply(df, evaluate.questions, function(x,y,z) 
evaluate.questions(df['Q1'],df['Q2'],df['Q3']))

Unfortunately this doesn't work and the problem appears that the sapply 
function is not feeding the parameters to the evaluate.questions 
function as I expect.  Can someone provide some guidance on what I am 
doing wrong?

This is the error message I am getting:

Error in x --1 :
   Comparison (1) is possible only for atomic and list types
In addition: warning messages:
In if (x == 1) { :
   the condition has length > 1 and only the first element will be used

        [[alternative HTML version deleted]]

______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.