Can I plot a linear regression with datetimes on the x-axis with seaborn?

Question

My DataFrame object looks like

            amount
date    
2014-01-06  1
2014-01-07  1
2014-01-08  4
2014-01-09  1
2014-01-14  1

I would li

Answer 1

Since Seaborn has trouble with dates, I'm going to create a work-around. First, I'll make the Date column my index:

# Make dataframe
df = pd.DataFrame({'amount' : [1,
                               1,
                               4,
                               1,
                               1]},
                  index = ['2014-01-06',
                           '2014-01-07',
                           '2014-01-08',
                           '2014-01-09',
                           '2014-01-14'])

Second, convert the index to pd.DatetimeIndex:

# Make index pd.DatetimeIndex
df.index = pd.DatetimeIndex(df.index)

And replace the original with it:

# Make new index
idx = pd.date_range(df.index.min(), df.index.max())

Third, reindex with the new index (idx):

# Replace original index with idx
df = df.reindex(index = idx)

This will produce a new dataframe with NaN values for the dates you don't have data:

Fourth, since Seaborn doesn't play nice with dates and regression lines I'll create a row count column that we can use as our x-axis:

# Insert row count
df.insert(df.shape[1],
          'row_count',
          df.index.value_counts().sort_index().cumsum())

Fifth, we should now be able to plot a regression line using 'row_count' as our x variable and 'amount' as our y variable:

# Plot regression using Seaborn
fig = sns.regplot(data = df, x = 'row_count', y = 'amount')

Sixth, if you would like the dates to be along the x-axis instead of the row_count you can set the x-tick labels to the index:

# Change x-ticks to dates
labels = [item.get_text() for item in fig.get_xticklabels()]

# Set labels for 1:10 because labels has 11 elements (0 is the left edge, 11 is the right
# edge) but our data only has 9 elements
labels[1:10] = df.index.date

# Set x-tick labels
fig.set_xticklabels(labels)

# Rotate the labels so you can read them
plt.xticks(rotation = 45)

# Change x-axis title
plt.xlabel('date')

plt.show();

Hope this helps!