Matplotlib Plot and Colorbar issues

Question

I have the below plot, however, I am struggling with the 3 questions below....

1. How can I move X-axis labels (1-31) to the top of the plot?
2. How can I change formating of the color bar from (7000 to 7k etc.)
3. How can I change the color from gray to another cmap like "Reds"?
4. Can I change the figure size? plt.figure(figsize=(20,10)) does not work?

data1 = pd.read_csv("a2data/data1.csv")
data2 = pd.read_csv("a2data/data2.csv")
merged_df = pd.concat([data1, data2])
merged_df.set_index(['month', 'day'], inplace=True)
merged_df.sort_index(inplace=True)
merged_df2=merged_df.groupby(['month', 'day']).deaths.mean().unstack('day')   
plt.imshow(merged_df2)
plt.xticks(np.arange(merged_df2.shape[1]), merged_df2.columns)
plt.yticks(np.arange(merged_df2.shape[0]), merged_df2.index)
plt.colorbar(orientation="horizontal")
plt.show()

Answer 1

Let's try:

# create a single subplot to access the axis
fig, ax = plt.subplots()

# passing the `cmap` for custom color
plt.imshow(df, cmap='hot', origin='upper')

# draw the colorbar
cb = plt.colorbar(orientation="horizontal")

# extract the ticks on colorbar
ticklabels = cb.get_ticks()

# reformat the ticks
cb.set_ticks(ticklabels)
cb.set_ticklabels([f'{int(x//1000)}K' for x in ticklabels])

# move x ticks to the top
ax.xaxis.tick_top()

plt.show()

Output:

Answer 2

Try this to invert the y axis:

ax = plt.yticks(np.arange(merged_df2.shape[0]), merged_df2.index)
plt.colorbar(orientation="horizontal")
ax.invert_yaxis()
plt.show()

I think for the color, you can find better in the pyplot documentation, https://matplotlib.org/3.3.1/api/_as_gen/matplotlib.pyplot.plot.html#matplotlib.pyplot.plot