Plot one series for one column with Polars dataframe and Plotly

Question

I can't find how to plot these two series A and B with time on X.

from numpy import linspace
import polars as pl
import plotly.express as px

import plotly.io as pio
pio.renderers.default = 'browser'

times = linspace(1, 6, 10)
df = pl.DataFrame({
    'time': times,
    'A': times**2,
    'B': times**3,
})

fig = px.line(df)
fig.show()

Data keep showing as 10 series with 3 points, instead of 2 series with 10 points and the first column as X values.

Edit:

This line:

fig = px.line(df, x='time', y=['A', 'B'])

produces this error:

ValueError: Value of 'x' is not the name of a column in 'data_frame'. Expected one of [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] but received: time

Using polars 0.15.0 and plotly 5.11.0

Hamzah Al-Qadasi · Accepted Answer · 2022-12-04 18:29:57Z

2

You use Polars Dataframe instead of Pandas dataframe and indexing is a little different here and what is why you have this error. In order to plot it, one way to do it is to convert the dataframe from Polars to Pandas on the fly by using to_pandas():

fig = px.line(df.to_pandas(),x='time', y=['A', 'B'])

Output

You can also use this way:

fig = px.line(x=df['time'], y=[df["A"],df["B"]])

edited Dec 4, 2022 at 18:29

answered Dec 4, 2022 at 18:05

Hamzah Al-Qadasi

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5 Comments

mins Over a year ago

Plotly is not compatible with Polars?

Hamzah Al-Qadasi Over a year ago

@mins no, Plotly is compatible with Polars, but you should select the columns correctly. Also, as you see in the second method, we do not need to convert our dataframe to Pandas dataframe.

mins Over a year ago

Ah, my mistake, I didn't see the second option. That's perfect. With the second option, my legend has names like 'wide_variable_0' instead of 'A', do you know why?

Hamzah Al-Qadasi Over a year ago

@mins It is recommended by the author of Plotly is to convert it to Pandas dataframe, please read this github.com/plotly/plotly.py/issues/3637#issuecomment-1245495678

Hamzah Al-Qadasi Over a year ago

@mins , the reason of why these names in the legend are because you pass a list to y parameter and Plotly cannot infer the labels of lines from the list. Thus, Plotly label each line by default names. (wide_variable_)

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