Include zero frequencies in frequency table for Likert data
I have a dataset with responses to a Likert item on a 9pt scale. I would like to create a frequency table (and barplot) of the data but some values on the scale never occur in my dataset, so table() removes that value from the frequency table. I would like it instead to present the value with a frequency of 0. That is, given the following dataset
# Assume a 5pt Likert scale for ease of example
data <- c(1, 1, 2, 1, 4, 4, 5)
I would like to get the following frequency table without having to manually insert a column named 3 with the value 0.
1 2 3 4 5
3 1 0 2 1
I'm new to R, so maybe I've overlooked something basic, but I haven't come across a function or option that gives the desired result.
Answer
EDIT:
tabular produces frequency tables while table produces contingency tables. However, to get zero frequencies in a one-dimensional contingency table as in the above example, the below code still works, of course.
This question provided the missing link. By converting the Likert item to a factor, and explicitly specifying the levels, levels with a frequency of 0 are still counted
data <- factor(data, levels = c(1:5))
table(data)
produces the desired output