Graphing non-numeric data in bar charts

Not everything is numeric, and often non-numeric data has to be handled differently, as we saw in the chapter on statistics and the chapter on data mining. For example, a scatter plot doesn't make much sense unless the data is naturally ordered in some way.

In this recipe, we'll use a bar chart to display how many items have a possible value each for a field of categorical data.

Getting ready

We'll use the same dependencies in our project.clj file as we did in Creating scatter plots with Incanter.

We'll also use this set of imports in our script or REPL:

(require '[incanter.core :as i]
         '[incanter.charts :as c]
         '[incanter.io :as iio])

For this chart, we'll use the mushroom dataset from the UCI machine learning archive. The web page with the information about this dataset is at http://archive.ics.uci.edu/ml/datasets/Mushroom, and we can download a copy of it with the header names directly from http...