Percentage calculation snippet

calc_percent.r

# Calculate percent of responses by department
    
# The input here is a subset of kano_questions - all of the 
# responses related to one item
x_by_dept <- ddply(subset(x, !is.na(department)),  # Dropping that person with no department
                   .var = "department", # I'm going to split x by department
                   .fun = function(y) {   # Writing a custom, nameless function to apply
                                          # to each chunk of x
                                          
                                          
    # The best way to see how this works is to make your own y
    # with y <- subset(x, department %in% "CS") and
    # step through each of the code bits below - then look
    # at the output of each. What does y look like?

    # First, I want to know how many respondents found this item
    # Attractive, Must-be, etc. This is a quick way to aggregate
    # their responses. y is the subset of x with just one
    # department's responses in it; "kano_cat" is the variable I'm
    # counting.
    dept_count <- count(y, "kano_cat")  
    
    # What does dept_count look like?

    # Now I'll add proportion who gave each response. 
    # mutate() is one way to do this, but the main 
    # thing is that I'm calculating the proportion
    # by dividng the column of counts (freq) by
    # the total number of respondents.
    # Since this is the last "object" produced
    # in the function, I don't bother to assign it;
    # R will just return it up to ddply, which will
    # stack the outputs of all the groups together
    # nicely.
    mutate(dept_count,
           prop = freq / sum(freq)
    )

})