Stacked Bar Chart With Selection Using Altair in Python
In this article, We will see Stacked Bar Chart With Selection with Altair python. It is a declarative and interactive visualization tool for Python, based on Visualization Grammar (VeGa), It is simple, user-friendly, and moreover provides clearly interpretable charts. It supports a wide variety of charts like bar, line, scatter, box, violin, and other charts in an interactive way. Let’s discuss how to create a stacked bar chart with a selection to highlight a particular stack of the bar chart.
The following command can be used to install Altair and Pandas like any other python library:
pip install altair pip install pandas pip install altair_viewer
- The altair.selection_single() specify the type of selection inside the select method. The method takes parameters that are discussed below.
Syntax: altair.selection_single(type, encodings)
- type – string. Determines the default event processing and data query for the selection. Three types single, multi (shift+ click), interval (drag).
- encodings – List of encoding channels. The corresponding data field values must match for a data tuple to fall within the selection.
- The encode() method is used to map columns to visual attributes of the plot. This method takes in parameters of the x and y-axis and other chart attributes. The mark property is what specifies how exactly those attributes should be represented on the plot.
Syntax: alt.Chart(data).mark_bar().encode(x, y, color)
- x – The x-axis value
- y – The y-axis value
- color – The color of the mark
Import the Altair and pandas package. Read the dataset using pandas and specify the type of selection we have used the selection_single() method. Then, pass the dataset to the chart() function and make use of the mark_bar().encode() method to pass the x and y-axis values and append the selection object after passing the parameters to the mark_bar() function.
The dataset used for demonstration purposes can be downloaded from here.
To see the interactive visualization, run the code and it will automatically redirect you to an interactive webpage.
The pandas DataFrame is used for demonstration purposes.