Visualizing fashion MNIST

In this exercise, we are going to visualize an example image of the fashion MNIST dataset. Basically, we are going to plot the 28x28 pixels values.

To do this we use:

A custom ggplot theme named plot_theme.
A data structure named xy_axis where the pixels values are stored.
A character vector named class_names with the names of each class.

The fashion_mnist dataset with 500 examples is available in the workspace. The `ggplot2 package is loaded.

Note that you can access the definition of the custom theme by typing plot_theme in the console.

Paste xy_axis together with the transpose of the 500th element from fashion_mnist using cbind().
Show the first 6 elements of plot_data.
Plot the example stored in plot_data using the correct index to get the class name as title.