Line charts show the change over time for one or more series (sales per hour). The line connects each data point in the series (shown or not). The y-axis baseline should be equal or less than the minimum value in the data.
• Show four or fewer series of lines on a line chart (Wong, 2010).
• Label each series directly or use an ordered legend.
Sosulski, Kristen. Data Visualization Made Simple (p. 55). Taylor and Francis. Kindle Edition.