Dropping levels

The contingency table from the last exercise revealed that there are some levels that have very low counts. To simplify the analysis, it often helps to drop such levels.

In R, this requires two steps: first filtering out any rows with the levels that have very low counts, then removing these levels from the factor variable with droplevels(). This is because the droplevels() function would keep levels that have just 1 or 2 counts; it only drops levels that don't exist in a dataset.

The contingency table from the last exercise is available in your workspace as tab.

Load the dplyr package.
Print tab to find out which level of align has the fewest total entries.
Use filter() to filter out all rows of comics with that level, then drop the unused level with droplevels(). Save the simplified dataset as comics_filtered.

Exercise

Dropping levels

Instructions