How to create a Calendar Heatmap using Matplotlib in Python

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by Abdul Rawoof A R dot icon Updated: May 4, 2023

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Calendar Heatmap plots Pandas time series data display over a conventional calendar year. We can share the days, weeks, and years on a light-to-gradient basis. It depends on the numeric value provided to the visualization in Python. We can use the Calendar Heat maps in different forms of analytics. But we use it to show user behavior on specific webpages templates. 


Calendar Heatmaps can help visualize our data, presented in a tabular structure. In the same instance, we will display calendar heat maps over a calendar view. It can be many weeks, the whole year, day of the week, and it will help us identify daily and weekly patterns. The main features of a calendar map are that it shows a color-coded overlay of mouse and tap movement on a website. The popularity of page elements displays a color scale from red to blue. We are using Pandas dataframe here for faster and easier dataframes. These are powerful than tables and spreadsheets as they are integral to NumPy and Python. 


A tabular structure with rows and columns is a pandas data frame's format. We can visualize part of a whole relationship and fit it into a calendar's cell as a pie chart. We can use the calendar heat maps to show the relationship between two axis variables. A cell's color can correspond to all metrics, like a frequency count of points in each bin statistic. Each cell reports a numeric count, like in a standard data table though the count. We can accompany it by color, with larger counts associated with darker colorings. To colormap names or objects, we use cmap, which maps the data values to the color space. 

How we can use calendar heat maps: 

1. By looking at the visualization. 

2. By reviewing the raw data points. 

Seaborn

  • We can use it to make better charts, thanks to its heatmap () function. 
  • The benefit of a calendar heat map is that it visualizes the volume of locations or events within a dataset. 
  • It directs viewers toward data visualization areas that matter most. This section starts with a post explaining the usage of the function based on any data input. 

Matplotlib

  • It is for creating static, animated, and interactive visualizations. 
  • It creates publication-quality plots. It makes interactive figures that can update, zoom, and pan. It will make the easy and hard things possible. 

Application of Heatmap

  • We can use it to show user behavior on specific web pages or project templates.
  • It can show where we have clicked on a page and how far they have scrolled down or used to show the results.

Features of Calendar Heatmap

Calendar Heatmap visualizes time-series data display over a conventional calendar year. We can shade the days, weeks, and years on a light gradient. We can do it based on the numeric value provided to the visualization in Python. 

Purpose of Calendar Heatmap

We can present the data using the calendar heatmap. It allows us to consume information or data to make more sense. It conveys through a 2-dimensional data representation in which different colors represent values. It offers an immediate visual summary of information. To implement this calendar heatmap, we need four important libraries that follow below. 

  1.  Matplotlib.
  2.  Seaborn.
  3.  Pandas.
  4.  NumPy.

Advantages

  • Spotting patterns at the month, day, and week levels is easy.
  • The cell size is arbitrary but large enough to be visible.

Disadvantages

  • Incorrect use of heat maps.
  • Use of additional methods.
  • Data interpretation may be less in-depth than we required.


Here is an example of building a Calendar Heatmap using Matplotlib in Python:

Fig: Preview of the output that you will get on running this code from your IDE.

Code

In this solution we're using Matplotlib, seaborn, Pandas and NumPy libraries.

import matplotlib.pyplot as plt
import seaborn as sns
import pandas as pd
import numpy as np

months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
df = pd.DataFrame({'month': np.random.choice(months, 1000), 'year': np.random.randint(1975, 2019, 1000)})
pivoted = df.pivot_table(index='month', columns='year', aggfunc=len, fill_value=0)
pivoted = pivoted.loc[months]  # change the order of the rows to be the same as months
for _ in range(20):
    # set some random locations to "not filled in"
    pivoted.iloc[np.random.randint(0, len(pivoted)), np.random.randint(0, len(pivoted.columns))] = np.nan
max_val = np.nanmax(pivoted.to_numpy())
ax = sns.heatmap(pivoted, cmap=plt.get_cmap('Greys', max_val + 1), vmin=-0.5, vmax=max_val + 0.5)
ax.patch.set_facecolor('white')
ax.patch.set_edgecolor('black')  # will be used for hatching
ax.patch.set_hatch('xxxx')
ax.collections[0].colorbar.outline.set_linewidth(1) # make outline visible
plt.tight_layout()
plt.show()

import matplotlib.pyplot as plt
import seaborn as sns
import pandas as pd
import numpy as np

# read the dataframe from a .csv file
pivoted = pd.read_csv('test.csv', index_col=0) # maybe: delimiter=';'
# extend the index to include all intermediate years
pivoted = pd.DataFrame(pivoted, index=range(pivoted.index.min(), pivoted.index.max() + 1))
# exchange columns and rows
pivoted = pivoted.T 
max_val = np.nanmax(pivoted.to_numpy())
ax = sns.heatmap(pivoted, cmap=plt.get_cmap('Greys', max_val + 1), vmin=-0.5, vmax=max_val + 0.5,
                 cbar_kws={'ticks': np.arange(max_val+1)})
ax.patch.set_facecolor('white')
ax.patch.set_edgecolor('black')  # will be used for hatching
ax.patch.set_hatch('xxxx')
ax.collections[0].colorbar.outline.set_linewidth(1) # make outline visible
ax.collections[0].colorbar.outline.set_edgecolor('black')
plt.tight_layout()
plt.show()

Instructions

Follow the steps carefully to get the output easily.

  1. Install PyCharm Community Edition on your computer.
  2. Open terminal and install the required libraries with following commands.
  3. Install Matplotlib - pip install matplotlib.
  4. Install Seaborn - pip install seaborn.
  5. Install Pandas - pip install pandas.
  6. Install NumPy - pip install numpy.
  7. Create a new Python file(eg: test.py).
  8. Copy the snippet using the 'copy' button and paste it into that file.
  9. Run the file using run button.


I hope you found this useful. I have added the link to dependent libraries, version information in the following sections.


I found this code snippet by searching for 'create heatmap plot' in kandi. You can try any such use case!

Environment Tested

I tested this solution in the following versions. Be mindful of changes when working with other versions.

  1. The solution is created in PyCharm 2022.3.3.
  2. The solution is tested on Python 3.9.7.
  3. Matplotlib version 3.7.1.
  4. Seaborn version v0.12.2.
  5. Pandas version v2.0.0.
  6. NumPy version v1.24.2.


Using this solution, we are able to create calendar heatmap using Matplotlib in Python with simple steps. This process also facilities an easy way to use, hassle-free method to create a hands-on working version of code which would help us to create calendar heatmap using Matplotlib in Python.

Dependent Libraries

matplotlibby matplotlib

Python doticonstar image 17559 doticonVersion:v3.7.1doticon
no licences License: No License (null)

matplotlib: plotting with Python

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            matplotlibby matplotlib

            Python doticon star image 17559 doticonVersion:v3.7.1doticonno licences License: No License

            matplotlib: plotting with Python
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                      seabornby mwaskom

                      Python doticonstar image 10797 doticonVersion:v0.12.2doticon
                      License: Permissive (BSD-3-Clause)

                      Statistical data visualization in Python

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                                seabornby mwaskom

                                Python doticon star image 10797 doticonVersion:v0.12.2doticon License: Permissive (BSD-3-Clause)

                                Statistical data visualization in Python
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                                          pandasby pandas-dev

                                          Python doticonstar image 38689 doticonVersion:v2.0.2doticon
                                          License: Permissive (BSD-3-Clause)

                                          Flexible and powerful data analysis / manipulation library for Python, providing labeled data structures similar to R data.frame objects, statistical functions, and much more

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                                                    pandasby pandas-dev

                                                    Python doticon star image 38689 doticonVersion:v2.0.2doticon License: Permissive (BSD-3-Clause)

                                                    Flexible and powerful data analysis / manipulation library for Python, providing labeled data structures similar to R data.frame objects, statistical functions, and much more
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                                                              numpyby numpy

                                                              Python doticonstar image 23755 doticonVersion:v1.25.0rc1doticon
                                                              License: Permissive (BSD-3-Clause)

                                                              The fundamental package for scientific computing with Python.

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                                                                        numpyby numpy

                                                                        Python doticon star image 23755 doticonVersion:v1.25.0rc1doticon License: Permissive (BSD-3-Clause)

                                                                        The fundamental package for scientific computing with Python.
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                                                                                  FAQ:  

                                                                                  What is a Calendar Heat map, and how does it differ from other chart types? 

                                                                                  It only visualizes time series data displayed over a conventional calendar year. It is better than other types. It is better to present trends in dimensions that have more variables. 


                                                                                  How can I use Seaborn to create a Calendar Heat map for my series data? 

                                                                                  Using Seaborn, we can annotate heatmaps that we can tweak. We can do it by using matplotlib tools per the creator's need. It integrates with Pandas data, and it helps us to explore and understand our data. 


                                                                                  Is there an easy way to visualize daily data with a Calendar Heat map? 

                                                                                  We can visualize a dataset's location or event volume. It will direct the viewers toward data visualization. It is because it matters most. 


                                                                                  What information will the day of the month column be in my data table? Will it provide me with a when visualizing my calendar heatmap? 

                                                                                  The month column provides us with months of the year with the data given by the user. 


                                                                                  Is there an ideal chart type to visualize calendar heatmaps created with Python? 

                                                                                  A 2D visual representation of data is where we can encode values in colors. It will deliver where a convenient and insightful view of information. 

                                                                                  You can also search for any dependent libraries on kandi like 'Matplotlib', 'Seaborn', 'Pandas' and 'NumPy'.

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