Artlo in Altair

Altair is the python interface to the declarative Vega visualization library.

There are many differences between altair and matplotlib, but one important difference is Encoding Data Types. For altair, it is important to know the difference between these types and when to use them as they effect the color and representation of your data.

To enable a salo style:

import altair as alt
import artlo

artlo.plot.set_alt_style('salo-dark')

Create some testing data:

path = gpd.datasets.get_path('naturalearth_lowres')
df = gpd.read_file(path)
df['c_var'] = np.random.random(df.shape[0])
df['d_var'] = np.random.choice(['a', 'b', 'c', 'd'], size=df.shape[0])

Without providing any styling options to a plot you will get the style's defaults:

alt.Chart(df).mark_geoshape().encode(
    'c_var:Q',
).project(
    'orthographic'
)

Here is the same default, but using the nominal encoding on a discrete variable:

alt.Chart(df).mark_geoshape().encode(
    'd_var:N',
).project(
    'orthographic'
)

You can also use a salo custom color palette:

alt.Chart(df).mark_geoshape().encode(
    color=alt.Color(
        'c_var:Q',
        scale=alt.Scale(range=artlo.color.palettes['titan'])
    )
).project(
    'orthographic'
)

salo-dark

artlo.plot.set_alt_style('salo-dark')

---

salo-light

artlo.plot.set_alt_style('salo-light')

---

cfo-light

artlo.plot.set_alt_style('cfo-light')

---

For reference, here is the default altair plotting style:

---

Code documentation

Lists the available altair plotting styles.

Returns:

Name	Type	Description
styles		list of style names to pass to plot.set_alt_style()

Source code in artlo/plot.py

def get_alt_styles():
    """Lists the available altair plotting styles.

    Args:
        None.

    Returns:
        styles: list of style names to pass to `plot.set_alt_style()`
    """

    if altairstyles is not None:
        themes = altairstyles.alt.themes.names()
        return themes
    else:
        return None

Sets a series of altair plot style parameters.

Parameters:

Name	Type	Description	Default
style		str of the style name to use. from plot.get_alt_styles()	required

Returns:

Type	Description
	None. Updates altair.themes

Source code in artlo/plot.py

def set_alt_style(style):
    """Sets a series of altair plot style parameters.

    Args:
        style: str of the style name to use. from `plot.get_alt_styles()`

    Returns:
        None. Updates altair.themes
    """

    if altairstyles is not None:
        altairstyles.alt.themes.enable(style)