How to annotate a gridded plot with values from a dict

Question

I have this Matplotlib grid and would like to write text in each of the grid cells. The text is provided by a dictionary. How would I do this?

Here's what I have so far:

fig, ax = plt.subplots()
plt.xlim(0, 3)
plt.ylim(3, 0)
plt.grid(True)
plt.xticks(np.arange(0, 4, 1.0))
plt.yticks(np.arange(0, 4, 1.0))

dictionary = {0: {'down': 58, 'right': 43, 'up': 9, 'left': 2},
              1: {'down': 23, 'right': 35, 'up': 1, 'left': 1},
              2: {'down': 4,  'right': 23, 'up': 0, 'left': 1},
              3: {'down': 21, 'right': 24, 'up': 1, 'left': 0},
              4: {'down': 24, 'right': 31, 'up': 2, 'left': 1},
              5: {'down': 6,  'right': 46, 'up': 1, 'left': 0},
              6: {'down': 25, 'right': 2, 'up': 1,  'left': 0 },
              7: {'down': 54, 'right': 4, 'up': 1,  'left': 1},
              8: {'down': 0,  'right': 0, 'up': 0,  'left': 0}
             }

The grid looks like this:

The grid cells are labeled 0 through 8, going vertically column wise (cell 2 is bottom left corner not top right corner). What I would like is to display the associated key-value pairs for each cell index, in the grid itself (like taking a pen and writing in the values in the appropriate cells, except programmatically).

Obviously it might get a little packed, and in that case I can make the grid itself bigger. But is there a way to display the text from the dictionary onto the grid, at each corresponding cell?

Trenton McKinney · Accepted Answer · 2021-11-08T19:48:47.440

Create a list of tuples for the (x, y) locations of the annotations using a list comprehension.
- Down and Across: [(x + 0.05, y + 0.5) for x in range(3) for y in range(3)]
- Across and Down: [(x + 0.05, y + 0.5) for y in range(3) for x in range(3)]
zip the position to the dict values, and add text with matplotlib.pyplot.text or matplotlib.axes.Axes.text

import matplotlib.pyplot as plt

fig, ax = plt.subplots(figsize=(12, 4))
ax.set_xlim(0, 3)
ax.set_ylim(3, 0)
ax.grid(True)
ax.set_xticks(np.arange(0, 4, 1.0))
ax.set_yticks(np.arange(0, 4, 1.0))

dictionary = {0: {'down': 58, 'right': 43, 'up': 9, 'left': 2},
              1: {'down': 23, 'right': 35, 'up': 1, 'left': 1},
              2: {'down': 4,  'right': 23, 'up': 0, 'left': 1},
              3: {'down': 21, 'right': 24, 'up': 1, 'left': 0},
              4: {'down': 24, 'right': 31, 'up': 2, 'left': 1},
              5: {'down': 6,  'right': 46, 'up': 1, 'left': 0},
              6: {'down': 25, 'right': 2, 'up': 1,  'left': 0},
              7: {'down': 54, 'right': 4, 'up': 1,  'left': 1},
              8: {'down': 0,  'right': 0, 'up': 0,  'left': 0}}

# create tuples of positions
positions = [(x + 0.05, y + 0.5) for x in range(3) for y in range(3)]

# add text
for (x, y), (k, v) in zip(positions, dictionary.items()):
    ax.text(x, y, f'{k}: {v}', color='purple')

How to annotate a gridded plot with values from a dict

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