A chart is an answer, not a decoration. Pick the comparison the reader needs to make, then choose the mark that makes that comparison easy. Bars compare lengths, lines show change over an ordered axis, and a pie forces the hardest comparison of all.
About 1 min of reading
Before this new lesson, one small question about the lesson you just finished. Recall it, do not look it up.
Print a proportional text bar chart.
Scale to a fixed width
Before you run it, say out loud what it will print. Then open the answer.
Notice the tiny bar
Before you run it, say out loud what it will print. Then open the answer.
Before you write anything, put these lines back in the right order. Click a line to move it up one step. This support step is easier than writing code from scratch, and it is here to make the last example stick.
Read the first example one line at a time. A line that prints shows what appears on screen; the rest set things up quietly.
A bar chart that starts at the minimum value makes a 5 percent difference look like a 90 percent difference. Bars must start at zero; lines may not, but then say so in the title.
Write the sentence the chart is meant to support above it. If you cannot write that sentence, the chart is exploratory and should not be in the report.
Bars share a baseline, so lengths compare reliably. Sort them by size. This is the default choice for 'which is biggest' questions and it works in black and white.
Time goes on the x axis in order, so a line shows trend and seasonality that a table hides. Use one line per series and no more than a handful, or the chart becomes a tangle.
Printing 'region ......... 412' with proportional dots is a legitimate chart for a terminal or a report. Reaching for a plotting library before you have checked the numbers is where charts go wrong.
Each one is defined here on this site. Open the entry for the full definition and the other words it points at.