Data Science Desktop Survival Guide
by Graham Williams
Bar Chart Basic
A common and simple plot is the bar chart which displays bars with a height that corresponds to the number of observations having that value of the variable displayed on the x-axis. We use ggplot2::geom_bar() to add a bar chart layer to a plot. Only an x-axis aesthetic is required using ggplot2::aes() with the x= option. The y-axis is automatically computed.
In our example we pipe the dataset on to ggplot2::ggplot(), specifying the x-axis as the categoric variable wind_dir_3pm (the x-axis). The count is automatically determined from the dataset by ggplot2::geom_bar() which then adds the layer of bars to the plot.
The y-ticks use commas with ggplot2::scale_y_continuous() using the labels=comma option. It is crucial that for large numbers commas separate the thousands, so that the reader is able to easily read the number. There can be catastrophic outcomes from a misreading of numbers.
The x-axis and y-axis labels are set using ggplot2::labs() with the x= and y= options. The x-label uses the original dataset's variable name as recorded in the template variable vname (i.e., WindDir3pm). The y-label is set to be Count.