Scatterplots¶
When to use a scatterplot¶
To show the relationship between two or more variables.
Style tips¶
When encoding more than two variables:
Use color to encode nominal variables. These are discrete categories.
Use size to encode quantitative variables. These are continuous variables like numbers.
import altair as alt
from vega_datasets import data
source = data.cars()
alt.Chart(source).mark_circle(size=60).encode(
x=alt.X('Horsepower'),
y=alt.Y('Miles_per_Gallon', title = "Miles per gallon"),
color=alt.Color('Origin'),
tooltip=['Name', 'Origin', 'Horsepower', alt.Tooltip('Miles_per_Gallon', title = "Miles per gallon")]
).properties(
title = "When encoding categories as a third variable use colors"
)
import altair as alt
from vega_datasets import data
source = data.iris()
alt.Chart(source).mark_circle().encode(
x = alt.X('sepalLength', title = "Sepal length (cm)", scale=alt.Scale(zero=False)),
y = alt.Y('sepalWidth', title="Sepal width (cm)", scale=alt.Scale(zero=False, padding=1)),
color = alt.Color('species', title = "Species"),
size = alt.Size('petalWidth', title = "Pedal width (cm)"),
tooltip = [
alt.Tooltip("species", title = "Species"),
alt.Tooltip("sepalLength", title = "Sepal Length (cm)"),
alt.Tooltip("sepalWidth", title = "Sepal Width (cm)"),
alt.Tooltip("petalWidth", title = "Petal Width (cm)")
],
).properties(
title = "When encoding quantities as a third variable use size"
)