Choosing a Chart

The shape of the question decides the shape of the picture.

Four questions, four charts

A quantity per category is a bar. A value over time is a line. A distribution is a histogram. A relationship between two measurements is a scatter. Most bad charts are one of these four answering a different question.

import pandas as pd

df = pd.DataFrame({"team": ["red", "blue"], "score": [90, 70]})
# A quantity per category: a bar chart of this table.
print(df.set_index("team")["score"].to_dict())

What the code looks like

pandas plots directly from a table. The plotting is one line; the work is the summary you feed it, which is why this unit grades the summary.

# df.plot(kind="bar", x="team", y="score")
# df.plot(kind="line", x="day", y="visits")
# df["score"].plot(kind="hist", bins=10)
print("the table you plot is the part that has to be right")

Exercise

Try It Yourself

Write chart_data(df) that returns the table behind a bar chart of mean score per team, as a dictionary of team to mean rounded to one decimal place.

import pandas as pd

def chart_data(df):
    # {team: mean score} -- the table a bar chart would draw.
    return {}

print(chart_data(pd.DataFrame({"team": ["red"], "score": [90]})))

Press Run to see output

Check Your Understanding

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