CODEWITHSUNDEEP
pythonstreamlitaltair
volkan
volkan

Reputation: 217

Altair Chart Conditional Text Opacity

Given the image below some values are smaller than 50. I want values smaller than 50 not to be on the chart.

Is it possible to hide, remove or shrink opacity for this?

enter image description here

Code is:

import altair as alt
from vega_datasets import data
import streamlit as st

source=data.barley()

bars = alt.Chart(source).mark_bar().encode(
    x=alt.X('sum(yield):Q', stack='zero'),
    y=alt.Y('variety:N'),
    color=alt.Color('site')
)

text = alt.Chart(source).mark_text(dx=-15, dy=3, color='white').encode(
    x=alt.X('sum(yield):Q', stack='zero'),
    y=alt.Y('variety:N'),
    detail='site:N',
    text=alt.Text('sum(yield):Q', format='.1f')
)

st.altair_chart(bars + text, theme="streamlit", use_container_width=True)

Upvotes: 1

Views: 459

Answers (1)

joelostblom
joelostblom

Reputation: 48909

You can use an aggregate transform to have access to the aggregated values in a condition and filter based on a threshold:

import altair as alt
from vega_datasets import data


base = alt.Chart(data.barley())

bars = base.mark_bar().encode(
    x=alt.X('sum(yield):Q', stack='zero'),
    y=alt.Y('variety:N'),
    color=alt.Color('site'),
)

text = base.mark_text(dx=-2, color='white', align='right').transform_aggregate(
    yield_sum='sum(yield)',
    groupby=['variety', 'site']
).encode(
    x=alt.X('yield_sum:Q', stack='zero'),
    y=alt.Y('variety:N'),
    text=alt.Text('yield_sum:Q', format='.0f'),
    opacity=alt.condition('datum.yield_sum > 50', alt.value(1), alt.value(0)),
    order='site'  # This is needed because the transform_aggregate return a different order of the values than the bar chart

)

bars + text

enter image description here

Upvotes: 1

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