Some random notes related to Plotly or Dash

Colour

See https://plotly.com/python/discrete-color/#discrete-colors-in-dash.

Plotly uses the colour sequence from the active template’s layout.colorway attribute.

• The default active template is plotly.
• You can choose from one of plotly’s built in qualitative colour sequences from the px.colors.qualitative module or define your own.

import plotly.express as px

fig = px.colors.qualitative.swatches()
fig.show()

Mapping colour to a ‘Month’ column

In the weather dataset I was mapping the colour to see how values changed over a year across all the weather stations in the dataset.

In order to use a discrete colour sequence when mapping colour to a variable such as a ‘month’ column, the month need to be in string format and not integer. Otherwise the colour will be mapped using a qualitative colour sequence.

It is useful to have a month name rather than just the month number for the legends of some plots.

A month name can be added to a dataframe from a date column using dt.month_name() as follows:

df['month'] = df['date'].dt.month_name()

• If there is a meaningful order to discrete/qualitative/categorical data then a continuous colour scale can be used as a discrete sequence.

For example: color_discrete_sequence= px.colors.sequential.Plasma_r