Visualisation & export — quiz

Why call savefig before show?

1. It is faster
2. show clears the figure, producing a blank file
3. savefig needs the window
4. Order does not matter

Answer: show clears the figure, producing a blank file — A classic cause of empty PNGs.

What does tight_layout fix?

1. Colours
2. Labels and titles being cropped
3. Slow rendering
4. Missing data

Answer: Labels and titles being cropped — It adjusts spacing so nothing is cut off.

Why must a bar chart y-axis start at zero?

1. Convention
2. Bar length encodes value, so truncation misleads
3. It errors otherwise
4. For colour scaling

Answer: Bar length encodes value, so truncation misleads — A truncated axis exaggerates small differences.

Which chart answers "are these two measures related"?

1. Line
2. Bar
3. Histogram
4. Scatter

Answer: Scatter — Scatter plots show relationships between two numeric measures.

Why does seaborn need long-form data?

1. It is faster
2. hue and col reference a column of categories
3. It cannot read wide data
4. To save memory

Answer: hue and col reference a column of categories — The grouping variable must be a column, not spread across columns.

Which shows median, quartiles and outliers per category?

1. Histogram
2. Box plot
3. Scatter
4. Heatmap

Answer: Box plot — Box plots compare distributions across categories.

Why pass index=False to to_csv?

1. It is faster
2. Otherwise the index becomes an unnamed extra column
3. It is required
4. To handle nulls

Answer: Otherwise the index becomes an unnamed extra column — That stray column compounds on every round trip.

For a chart going into a slide deck, prefer:

1. PNG at 72 dpi
2. SVG
3. JPG
4. PDF only

Answer: SVG — Vector output stays sharp at any size.