Style Line Plots using Matplotlib¶

Date published: 2018-03-04

Category: Data Visualizations

Subcategory: Matplotlib Plotting

Tags: line plot, datetime

This post will cover how to make some basic changes to Matplotlib line plots such as how to:

• Add a grid
• Add a horizontal dotted line
• Add a text label
• Add markers on plotted points
• Adjust line thickness

Import Modules¶

In [1]:

import matplotlib.pyplot as plt
import seaborn as sns
from datetime import datetime
% matplotlib inline

import matplotlib.pyplot as plt import seaborn as sns from datetime import datetime % matplotlib inline

Fitbit Activity Data¶

Below is my Fitbit activity of daily step count over a 15 day time period.

In [2]:

dates = ['2018-02-01', '2018-02-02', '2018-02-03', '2018-02-04',
         '2018-02-05', '2018-02-06', '2018-02-07', '2018-02-08',
         '2018-02-09', '2018-02-10', '2018-02-11', '2018-02-12',
         '2018-02-13', '2018-02-14', '2018-02-15']

dates = ['2018-02-01', '2018-02-02', '2018-02-03', '2018-02-04', '2018-02-05', '2018-02-06', '2018-02-07', '2018-02-08', '2018-02-09', '2018-02-10', '2018-02-11', '2018-02-12', '2018-02-13', '2018-02-14', '2018-02-15']

In [3]:

steps = [11178, 9769, 11033, 9757, 10045, 9987, 11067, 11326, 9976,
         11359, 10428, 10296, 9377, 10705, 9426]

steps = [11178, 9769, 11033, 9757, 10045, 9987, 11067, 11326, 9976, 11359, 10428, 10296, 9377, 10705, 9426]

Convert Date Strings to Datetime Objects¶

In [4]:

dates_list = [datetime.strptime(date, '%Y-%m-%d') for date in dates]

dates_list = [datetime.strptime(date, '%Y-%m-%d') for date in dates]

Initial Plot with Generic Plot Style Customizations¶

These initial styles could be applied to any type of plot - whether that be a scatter plot, line plot or a histogram.

In [5]:

plt.figure(figsize=(10, 8))
plt.plot(dates_list, steps, color='coral')
plt.title("Daily Step Count over Time", fontsize=18, y=1.02)
plt.xlabel("Day", fontsize=14, labelpad=15)
plt.ylabel("Daily Step Count", fontsize=14, labelpad=15)
plt.tick_params(labelsize=12, pad=6)
plt.xticks(rotation=25);

plt.figure(figsize=(10, 8)) plt.plot(dates_list, steps, color='coral') plt.title("Daily Step Count over Time", fontsize=18, y=1.02) plt.xlabel("Day", fontsize=14, labelpad=15) plt.ylabel("Daily Step Count", fontsize=14, labelpad=15) plt.tick_params(labelsize=12, pad=6) plt.xticks(rotation=25);

Add a Grid¶

Call the grid method and pass the value True to the b argument - b for boolean. This action includes a grid.

In the grid method, pass the value 0.5 to the linewidth argument to make thinner grid lines than usual.

In [6]:

plt.figure(figsize=(10, 8))
plt.plot(dates_list, steps, color='coral')
plt.title("Daily Step Count over Time", fontsize=18, y=1.02)
plt.xlabel("Day", fontsize=14, labelpad=15)
plt.ylabel("Daily Step Count", fontsize=14, labelpad=15)
plt.tick_params(labelsize=12, pad=6)
plt.xticks(rotation=25)
plt.grid(b=True, linewidth=0.5);

plt.figure(figsize=(10, 8)) plt.plot(dates_list, steps, color='coral') plt.title("Daily Step Count over Time", fontsize=18, y=1.02) plt.xlabel("Day", fontsize=14, labelpad=15) plt.ylabel("Daily Step Count", fontsize=14, labelpad=15) plt.tick_params(labelsize=12, pad=6) plt.xticks(rotation=25) plt.grid(b=True, linewidth=0.5);

Add Horizontal Dotted Line for Daily Step Goal¶

Call the axhline method and pass the following values to the arguments:

argument	value	description
y	10000	Horizontal line will be at y-coordinate of 10000 daily steps
color	green	Color of our horizontal line
linestyle	--	Dashed line style
linewidth	1.5	Thickness of line

In [7]:

plt.figure(figsize=(10, 8))
plt.plot(dates_list, steps, color='coral')
plt.title("Daily Step Count over Time", fontsize=18, y=1.02)
plt.xlabel("Day", fontsize=14, labelpad=15)
plt.ylabel("Daily Step Count", fontsize=14, labelpad=15)
plt.tick_params(labelsize=12, pad=6)
plt.xticks(rotation=25)
plt.grid(True)
plt.axhline(y=10000, color='green', linestyle='--', linewidth=1.5);

plt.figure(figsize=(10, 8)) plt.plot(dates_list, steps, color='coral') plt.title("Daily Step Count over Time", fontsize=18, y=1.02) plt.xlabel("Day", fontsize=14, labelpad=15) plt.ylabel("Daily Step Count", fontsize=14, labelpad=15) plt.tick_params(labelsize=12, pad=6) plt.xticks(rotation=25) plt.grid(True) plt.axhline(y=10000, color='green', linestyle='--', linewidth=1.5);

Text Label on Plot¶

We want to make clear that the horizontal line is our Daily Step Goal.

Call the text method and pass in the following arguments:

argument	value	description
x	dates_list[-1]	Start of text x-coordinate location at last x-tick value
y	10000	Text will be at y-coordinate of 10000 daily steps
s	Daily Step Goal	String of text
fontsize	1.5	Font size of text in pixels
bbox facecolor	whitesmoke	Background color of text box
bbox boxstyle	round, pad=0.4	Rounded corners text box with padding of 0.4px between text and box border

In [8]:

plt.figure(figsize=(10, 8))
plt.plot(dates_list, steps, color='coral')
plt.title("Daily Step Count over Time", fontsize=18, y=1.02)
plt.xlabel("Day", fontsize=14, labelpad=15)
plt.ylabel("Daily Step Count", fontsize=14, labelpad=15)
plt.tick_params(labelsize=12, pad=6)
plt.xticks(rotation=25)
plt.grid(True)
plt.axhline(y=10000, color='green', linestyle='--', linewidth=1.5)
plt.text(x=dates_list[-1], y=10000, s="Daily Step Goal", fontsize=14,
         bbox=dict(facecolor='whitesmoke', boxstyle="round, pad=0.4"));

plt.figure(figsize=(10, 8)) plt.plot(dates_list, steps, color='coral') plt.title("Daily Step Count over Time", fontsize=18, y=1.02) plt.xlabel("Day", fontsize=14, labelpad=15) plt.ylabel("Daily Step Count", fontsize=14, labelpad=15) plt.tick_params(labelsize=12, pad=6) plt.xticks(rotation=25) plt.grid(True) plt.axhline(y=10000, color='green', linestyle='--', linewidth=1.5) plt.text(x=dates_list[-1], y=10000, s="Daily Step Goal", fontsize=14, bbox=dict(facecolor='whitesmoke', boxstyle="round, pad=0.4"));

Add Markers on Plotted Points¶

In our plot method, pass the value o to the marker argument to create filled in plotted points on our line.

In [9]:

plt.figure(figsize=(10, 8))
plt.plot(dates_list, steps, color='coral', marker='o')
plt.title("Daily Step Count over Time", fontsize=18, y=1.02)
plt.xlabel("Day", fontsize=14, labelpad=15)
plt.ylabel("Daily Step Count", fontsize=14, labelpad=15)
plt.tick_params(labelsize=12, pad=6)
plt.xticks(rotation=25)
plt.grid(True)
plt.axhline(y=10000, color='green', linestyle='--', linewidth=1.5)
plt.text(x=dates_list[-1], y=10000, s="Daily Step Goal", fontsize=14,
         bbox=dict(facecolor='whitesmoke', boxstyle="round, pad=0.4"));

plt.figure(figsize=(10, 8)) plt.plot(dates_list, steps, color='coral', marker='o') plt.title("Daily Step Count over Time", fontsize=18, y=1.02) plt.xlabel("Day", fontsize=14, labelpad=15) plt.ylabel("Daily Step Count", fontsize=14, labelpad=15) plt.tick_params(labelsize=12, pad=6) plt.xticks(rotation=25) plt.grid(True) plt.axhline(y=10000, color='green', linestyle='--', linewidth=1.5) plt.text(x=dates_list[-1], y=10000, s="Daily Step Goal", fontsize=14, bbox=dict(facecolor='whitesmoke', boxstyle="round, pad=0.4"));

Make Line Thicker¶

In our plot method, pass a value greater than 2 to the linewidth argument to see a significantly thicker line. This often makes your line plots easier to see and interpret for viewers.

In [10]:

plt.figure(figsize=(10, 8))
plt.plot(dates_list, steps, color='coral', marker='o', linewidth=2.5)
plt.title("Daily Step Count over Time", fontsize=18, y=1.02)
plt.xlabel("Day", fontsize=14, labelpad=15)
plt.ylabel("Daily Step Count", fontsize=14, labelpad=15)
plt.tick_params(labelsize=12, pad=6)
plt.xticks(rotation=25)
plt.grid(True)
plt.axhline(y=10000, color='green', linestyle='--', linewidth=1.5)
plt.text(x=dates_list[-1], y=10000, s="Daily Step Goal", fontsize=14,
         bbox=dict(facecolor='whitesmoke', boxstyle="round, pad=0.4"));

plt.figure(figsize=(10, 8)) plt.plot(dates_list, steps, color='coral', marker='o', linewidth=2.5) plt.title("Daily Step Count over Time", fontsize=18, y=1.02) plt.xlabel("Day", fontsize=14, labelpad=15) plt.ylabel("Daily Step Count", fontsize=14, labelpad=15) plt.tick_params(labelsize=12, pad=6) plt.xticks(rotation=25) plt.grid(True) plt.axhline(y=10000, color='green', linestyle='--', linewidth=1.5) plt.text(x=dates_list[-1], y=10000, s="Daily Step Goal", fontsize=14, bbox=dict(facecolor='whitesmoke', boxstyle="round, pad=0.4"));