How to do it...

The following is the code block that plots a heatmap of the correlation matrix:

1. Read the data from a CSV file into a pandas DataFrame:

wine_quality = pd.read_csv('winequality.csv', delimiter=';')

2. Get the correlation matrix of all attributes of wine_quality:

corr = wine_quality.corr()

3. Specify the figure size:

plt.figure(figsize=(12,9))

4. Plot the heatmap:

plt.imshow(corr,cmap='hot')

5. Plot the colorbar to map which color represents which data values:

plt.colorbar()

6. Label the x and y axis ticks. Show the x axis labels with 20 degrees of rotation:

plt.xticks(range(len(corr)),corr.columns, rotation=20)
plt.yticks(range(len(corr)),corr.columns)

7. Display the plot on the screen:

plt.show()