Heatmap with plt.imshow in Matplotlib - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does plt.imshow() do in matplotlib?

plt.imshow() displays data as an image, where the data values are shown as colors in a grid. It is often used to create heatmaps.

beginner

How can you add a color bar to a heatmap created with plt.imshow()?

Use plt.colorbar() after plt.imshow() to add a color bar that shows the mapping between data values and colors.

beginner

What parameter controls the color scheme in plt.imshow()?

The cmap parameter controls the color map (color scheme) used to display the data. For example, cmap='viridis' or cmap='hot'.

intermediate

How do you control the interpolation method in plt.imshow()?

The interpolation parameter controls how pixel colors are calculated between data points. For example, interpolation='nearest' shows sharp blocks, while interpolation='bilinear' smooths colors.

beginner

Why might you use plt.imshow() instead of other plotting functions for heatmaps?

plt.imshow() is simple and fast for showing 2D arrays as images. It gives direct control over colors and interpolation, making it great for quick heatmaps.

Which function adds a color bar to a heatmap created with plt.imshow()?

A plt.legend()

B plt.title()

C plt.colorbar()

D plt.grid()

plt.colorbar() adds a color bar that shows the color scale for the heatmap.

What does the cmap parameter in plt.imshow() control?

A The color scheme used

B The size of the plot

C The data values

D The axis labels

cmap sets the color map, which defines the colors used to represent data values.

If you want sharp blocks of color in your heatmap, which interpolation should you use?

A bilinear

B nearest

C cubic

D spline

interpolation='nearest' shows each data point as a sharp colored block.

What type of data is best visualized with plt.imshow()?

A Categorical labels

B 1D lists

C Text data

D 2D arrays or matrices

plt.imshow() is designed to display 2D arrays as colored images.

Which of these is NOT a valid color map name for cmap?

A bluegreen

B hot

C viridis

D plasma

bluegreen is not a standard matplotlib color map name.

Explain how to create a heatmap using plt.imshow() including adding a color bar and choosing a color map.

Think about showing data as colors and how to explain the color meaning.

Describe the role of the interpolation parameter in plt.imshow() and how it affects the heatmap appearance.

Consider how pixels blend or stay distinct.