Analysis of multiple response

Your function is actually far too complicated for what you need to do. I think a function like this should work and be more flexible.

multfreqtable = function(data, question.prefix) {
  # Find the columns with the questions
  a = grep(question.prefix, names(data))
  # Find the total number of responses
  b = sum(data[, a] != 0)
  # Find the totals for each question
  d = colSums(data[, a] != 0)
  # Find the number of respondents
  e = sum(rowSums(data[,a]) !=0)
  # d + b as a vector. This is your overfall frequency 
  f = as.numeric(c(d, b))
  data.frame(question = c(names(d), "Total"),
             freq = f,
             percent = (f/b)*100,
             percentofcases = (f/e)*100 )
}

Add another question to your example dataset:

set.seed(1); df1$q2a = sample(c(0, 1), 30, replace=T)
set.seed(2); df1$q2b = sample(c(0, 2), 30, replace=T)
set.seed(3); df1$q2c = sample(c(0, 3), 30, replace=T)

Make a table for "q1" responses:

> multfreqtable(df1, "q1")
  question freq   percent percentofcases
1      q1a   15  33.33333             60
2      q1b   15  33.33333             60
3      q1c   15  33.33333             60
4    Total   45 100.00000            180

Make a table for "q2" responses:

> multfreqtable(df1, "q2")
  question freq   percent percentofcases
1      q2a   14  31.11111       53.84615
2      q2b   13  28.88889       50.00000
3      q2c   18  40.00000       69.23077
4    Total   45 100.00000      173.07692

Tables for multiple questions

Here's a modified version of the function that allows you to create a list of tables for multiple questions at once:

multfreqtable = function(data, question.prefix) {
  z = length(question.prefix)
  temp = vector("list", z)

  for (i in 1:z) {
    a = grep(question.prefix[i], names(data))
    b = sum(data[, a] != 0)
    d = colSums(data[, a] != 0)
    e = sum(rowSums(data[,a]) !=0)
    f = as.numeric(c(d, b))
    temp[[i]] = data.frame(question = c(sub(question.prefix[i], 
                                            "", names(d)), "Total"),
                           freq = f,
                           percent = (f/b)*100,
                           percentofcases = (f/e)*100 )
    names(temp)[i] = question.prefix[i]
  }
  temp
}

Examples:

> multfreqtable(df1, "q1")
$q1
  question freq   percent percentofcases
1        a   15  33.33333             60
2        b   15  33.33333             60
3        c   15  33.33333             60
4    Total   45 100.00000            180

> test1 = multfreqtable(df1, c("q1", "q2"))
> test1
$q1
  question freq   percent percentofcases
1        a   15  33.33333             60
2        b   15  33.33333             60
3        c   15  33.33333             60
4    Total   45 100.00000            180

$q2
  question freq   percent percentofcases
1        a   14  31.11111       53.84615
2        b   13  28.88889       50.00000
3        c   18  40.00000       69.23077
4    Total   45 100.00000      173.07692

> test1$q1
  question freq   percent percentofcases
1        a   15  33.33333             60
2        b   15  33.33333             60
3        c   15  33.33333             60
4    Total   45 100.00000            180