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

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
Read the documentation more closely: sapply(dataFrame, func)
applies func() to each column, not row, of dataFrame.
preferences <- sapply(df, evaluate.questions, function(x,y,z)
evaluate.questions(df['Q1'],df['Q2'],df['Q3']))
Furthermore,
    sapply(X = dataFrame, FUN = func, extraArgument)
calls
    func(dataFrame[, i], extraArgument)
for i in seq_len(ncol(dataFrame).

One problem is that FUN=evaluate.questions takes 3 arguments and
you give it only 2.  Another problem is that the third argument you
pass to sapply is a function (of 3 arguments) and FUN is not expecting
any of its arguments to be functions.

It may be easier for you to not use sapply here, but to use for-loops and
come up with something that works.  (Write tests that will indicate whether
it works or not in a variety of situations.)  Then transform it to use things
like ifelse() and sapply() to make it more readable and run faster.
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?
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
Of Walter Anderson
Sent: Friday, December 06, 2013 7:44 AM
To: r-help at r-project.org
Subject: [R] Need help figuring out sapply (and similar functions) with multiple parameter
user defined function

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]]

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

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