Heatmaps can have too long numeric labels

Often times, I have heatmaps like this:

I’d like for the numeric labels to be shorter. I eventually found a solution through this SO answer after looking at the source for keywords to google. This solution is nowhere as clean as I’d like.

d = [{'p1': p1, 'p2': p2, 'error': np.random.rand()}
     for p1 in np.logspace(0, 1, num=5)
     for p2 in np.logspace(0, 3, num=5)]

df = pd.DataFrame(d)
df = df.pivot(values='error', index='p1', columns='p2')

ax = sns.heatmap(df)

# format text labels
fmt = '{:0.2f}'
xticklabels = []
for item in ax.get_xticklabels():
    item.set_text(fmt.format(float(item.get_text())))
    xticklabels += [item]
yticklabels = []
for item in ax.get_yticklabels():
    item.set_text(fmt.format(float(item.get_text())))
    yticklabels += [item]

ax.set_xticklabels(xticklabels)
ax.set_yticklabels(yticklabels)

plt.show()

…which produces this plot:

[FlorianWilhelm]

@stsievert to really make this work with seaborn I had to overwrite the current FixedFormatter like

from matplotlib.ticker import FixedFormatter

ax = sns.heatmap(heat_data)
x_format = ax.xaxis.get_major_formatter()
x_format.seq = ["{:0.0f}".format(float(s)) for s in x_format.seq]
y_format = ax.yaxis.get_major_formatter()
y_format.seq = ["{:0.0f}".format(float(s)) for s in y_format.seq]
ax.xaxis.set_major_formatter(x_format)
ax.yaxis.set_major_formatter(y_format)

and then it worked.

[mwaskom]

There’s a number of ways to control this sort of thing. The matplotlib solution would be to use a tick formatter. Or you could do

ax = sns.heatmap(df,
                 xticklabels=df.columns.values.round(2),
                 yticklabels=df.index.values.round(2))