CODEWITHSUNDEEP
altair
Clinton B
Clinton B

Reputation: 51

How do you create a sortable bar chart in Altair 5?

How do you create a sortable bar chart in Altair 5 (i.e., sortable alphabetically by category, ascending by value, and descending by value) similar to this one in the D3 gallery?

When I use the following code:

import pandas as pd
import altair as alt

# Sample Data
data = pd.DataFrame({
    "Category": ["A", "B", "C", "D", "E"],
    "Value": [30, 10, 50, 20, 40]
})

# Create a selection parameter with a dropdown menu for sorting
sort_by = alt.param(
    name="sort_by", 
    bind=alt.binding_select(
        options=["Alphabetical", "Ascending", "Descending"], 
        name="Sort by: "
    ), 
    value="Alphabetical"  # Default value
)

# Define the sorting field using alt.when
sorting = alt.when(
    sort_by == "Alphabetical", "Category",
    alt.when(sort_by == "Ascending", "Value", "-Value")  # Descending as default
)

# Create the bar chart with dynamic sorting
chart = alt.Chart(data).mark_bar().encode(
    x=alt.X("Category:N", sort=sorting, title="Category"),
    y=alt.Y("Value:Q", title="Value"),
    color=alt.Color("Category:N", legend=None)
).add_params(sort_by).properties(width=500, height=400)

chart

I receive the following error message:

TypeError: Predicate composition is not permitted for 'str'.
Try wrapping 'Value' in a `Parameter` first.

Colab notebook: https://colab.research.google.com/drive/17OoguaVCKIKnGqTfIB-5tb2SfNDJgyjV?usp=sharing

Upvotes: 2

Views: 23

Answers (0)

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