Unfortunately, when it comes to time series data, I don't always find the convenience method convenient. I often have a sparse DataFrame with lots of NaNs, which are not ignored by the convenience method. Additionally, I don't like the way that matplotlib places the lines hard against the left and right-hand sides of the canvas. I like a little bit of space at each end of the chart. Finally, I like playing with the tick marks and tick labels to get the right density of information on the x-axis.
Rather than use the inconvenient convenience method, I regularly find myself writing a short function to produce the plot layout I find a little more aesthetically pleasing. An example chart (from Mark the Ballot) and the associated python code follows.
import datetime import pandas as pd import numpy as np import matplotlib.pyplot as plt from matplotlib.dates import DateFormatter, YearLocator, MonthLocator plt.style.use('ggplot') def plot(df, filename, heading=None): fig, ax = plt.subplots(figsize=(8, 4)) min_date = None max_date = None for col_name in df.columns.values: # plot the column col = df[col_name] col = col[col.notnull()] # drop NAs dates = [zzz.to_timestamp().date() for zzz in col.index] ax.plot_date(x=dates, y=col, fmt='-', label=col_name, tz=None, xdate=True, ydate=False, linewidth=1.5) # establish the date range for the data if min_date: min_date = min(min_date, min(dates)) else: min_date = min(dates) if max_date: max_date = max(max_date, max(dates)) else: max_date = max(dates) # give a bit of space at each end of the plot - aesthetics span = max_date - min_date extra = int(span.days * 0.03) * datetime.timedelta(days=1) ax.set_xlim([min_date - extra, max_date + extra]) # format the x tick marks ax.xaxis.set_major_formatter(DateFormatter('%Y')) ax.xaxis.set_minor_formatter(DateFormatter('\n%b')) ax.xaxis.set_major_locator(YearLocator()) ax.xaxis.set_minor_locator(MonthLocator(bymonthday=1, interval=2)) # grid, legend and yLabel ax.grid(True) ax.legend(loc='best', prop={'size':'x-small'}) ax.set_ylabel('Percent') # heading if heading: fig.suptitle(heading, fontsize=12) fig.tight_layout(pad=1.5) # footnote fig.text(0.99, 0.01, 'marktheballot.blogspot.com.au', ha='right', va='bottom', fontsize=8, color='#999999') # save to file fig.savefig(filename, dpi=125)
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