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DATA SCIENCE PYTHON PLAYGROUND

Data Foundations · A little practice goes a long way.

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Optional · figures and composition · V28 · 8 MIN

Annotate important points

Explain an observation directly on the chart.

Exercises within this concept

  1. FollowFollow the techniqueCurrent exercise
  2. ChangeAdapt a requirement
  3. TransferChoose and combine

Understand the idea

An annotation links text to a specific observation. Select the relevant row first so both coordinates describe the same point.

Concept sketch: arrow identifies the highest observationPeakarrow identifies the highest observation
Illustration · not the exercise output

A small example

xy=(2, 70) points to that data location; xytext=(8, 8) with offset points places text a little right and above it.

Follow the code

Apply the idea to the supplied table. Read from top to bottom; the final line displays the result.

import matplotlib.pyplot as plt
import seaborn as sns

fig, ax = plt.subplots(figsize=(6, 4))
sns.scatterplot(data=df, x="hours", y="score", ax=ax)
peak = df.loc[df["score"].idxmax()]
ax.annotate(
    "Peak",
    xy=(peak["hours"], peak["score"]),
    xytext=(8, 8),
    textcoords="offset points",
    arrowprops={"arrowstyle": "->"},
)
ax.set(title="Study club", xlabel="hours", ylabel="score")
fig.tight_layout()
plt.show()

What each part does

ax.annotate("Peak", xy=(x, y), ...)
label a point
idxmax()
row label of the largest value
arrowprops={"arrowstyle": "->"}
point an arrow at it

Your inputs

The editable setup on the right creates df. Run executes the setup and your work from top to bottom.

Study club · 8 synthetic rows
studentclubhoursscoregroup
AriArt152A
BoCode371A
CyArt265B
DeeCode482B
EliArt589A
FloCode376A
GusArt693B
HanCode261B

Your task · Follow

  1. Using df, scatter hours against score.
  2. Label the row with highest score "Peak", offset by (8, 8) points, with an arrow.
  3. Chart: title "Study club"; x "hours"; y "score".
  4. Use: annotate().
Hint

Find the target row, then use both coordinates from that same row for the annotation.

Reveal solution

One way to do it. Keep any supplied setup in the editor and use this in the Your work section.

import matplotlib.pyplot as plt
import seaborn as sns

fig, ax = plt.subplots(figsize=(6, 4))
sns.scatterplot(data=df, x="hours", y="score", ax=ax)
peak = df.loc[df["score"].idxmax()]
ax.annotate(
    "Peak",
    xy=(peak["hours"], peak["score"]),
    xytext=(8, 8),
    textcoords="offset points",
    arrowprops={"arrowstyle": "->"},
)
ax.set(title="Study club", xlabel="hours", ylabel="score")
fig.tight_layout()
plt.show()
Your task · Follow
  1. Using df, scatter hours against score.
  2. Label the row with highest score "Peak", offset by (8, 8) points, with an arrow.
  3. Chart: title "Study club"; x "hours"; y "score".
  4. Use: annotate().

Tab: indent · Shift+Tab: outdent · Esc, then Tab: leave editor

Edit Python. Control or Command plus Enter runs it. Tab indents by four spaces. Shift plus Tab outdents. Press Escape, then Tab or Shift plus Tab to leave the editor.

Each run executes all editor code in a fresh Python session. Display charts with plt.show().

Python starts when you open a lesson.

Output

Run your code to see what Python returns.