---
title: "Altair"
author: "Nobukuni Hyakutake"
date: "2025-04-24"
date-format: "iso"
categories: [Python]
image: "field_mustard.jpeg"
---
## 散布図
```{python}
# import altair with an abbreviated alias
import altair as alt
# load a sample dataset as a pandas DataFrame
from vega_datasets import data
cars = data.cars()
cars
```
```{python}
# make the chart
alt.Chart(cars).mark_point().encode(
x='Horsepower',
y='Miles_per_Gallon',
color='Origin',
).interactive()
```
```{python}
# make the chart
alt.Chart(cars).mark_point().encode(
x='Horsepower',
y='Miles_per_Gallon',
color='Origin',
)
```
## ヒストグラム
### Movies
```{python}
import altair as alt
from vega_datasets import data
source = data.movies.url
source
```
```{python}
alt.Chart(source).mark_bar().encode(
alt.X("IMDB_Rating:Q", bin=True),
y='count()',
)
```
### Penguins-Adelie
```{r}
library(tidyverse)
library(palmerpenguins)
df<-penguins |> drop_na()
write.csv(df,"penguins.csv",row.names = FALSE,na="")
```
```{python}
import polars as pl
import math
penguins=pl.read_csv("penguins.csv")
penguins
```
```{python}
penguins_adelie=penguins.filter(pl.col("species")=="Adelie")
penguins_adelie
```
```{python}
g_width=100
g_height=g_width*2/(1+math.sqrt(5))
chart=alt.Chart(penguins_adelie).mark_bar().encode(
alt.X("bill_length_mm", bin=True),
y='count()',
).properties(
width=g_width,
height=g_height)
chart
chart.save('penguins_adelie.png', ppi=200)
```
保存したファイルを表示
### Penguins-Facet by species
```{python}
penguins=penguins.with_columns(pl.lit(48).alias("a"))
chart1=alt.Chart(penguins).mark_bar().encode(
alt.X("bill_length_mm").bin(),
y="count()",
row="species"
).properties(
width=g_width*1.5,
height=g_height*1.5)
chart1
chart1.save('penguins_facet.png', ppi=200)
```
保存したファイルを表示
```{python}
chart1=alt.Chart().mark_bar().encode(
alt.X("bill_length_mm").bin(),
y="count()",
).properties(
width=g_width*1.5,
height=g_height*1.5)
chart2=alt.Chart().mark_rule().encode(
x="a"
)
chart=(chart1+chart2).facet(row="species",data=penguins)
chart
chart.save('penguins_facet_vline.png', ppi=200)
```
保存したファイルを表示
## 参考文献
- [Simple Histogram](https://altair-viz.github.io/gallery/simple_histogram.html)
- [Faceted Histogram](https://altair-viz.github.io/gallery/distributions_faceted_histogram.html)
- [Saving Altair Charts](https://altair-viz.github.io/user_guide/saving_charts.html)
- [add vertical line faceted chart](https://github.com/vega/altair/issues/1124#issuecomment-417712132)
## Python version
```{python}
import platform
"Python version "+platform.python_version()
```
