Heatmap categorical axis not recognized as categorical

[plpla]

I was trying to create an heat-map offline and the categorical axis is not recognized properly.
In the following example, the X axis is interpreted as numerical values and the heat-map is empty.

import plotly.graph_objs as go
from plotly.offline import init_notebook_mode, iplot
import plotly
print(plotly.__version__)    #3.7.1
init_notebook_mode()

trace = go.Heatmap(z=np.random.rand(2, 9), y=["A", "B"], x=["1E1", "2A1", "3E2", "2A2", "1A1", "3A1", "1E2", "3E3", "1A2"],  colorscale="Viridis")
iplot([trace])

[jonmmease]

Thanks for the report @plpla,

This seems to be an issue with the Plotly.js logic for automatically choosing the axis type. The workaround is be explicit that you want a categorical x-axis

import plotly.graph_objs as go
import numpy as np

from plotly.offline import init_notebook_mode, iplot
import plotly
print(plotly.__version__)    #3.7.1
init_notebook_mode()

trace = go.Heatmap(z=np.random.rand(2, 9),
                   y=["A", "B"],
                   x=["1B1", "2A1", "3E2", "2A2", "1A1", "3A1", "1E2", "3E3", "1A2"],
                   colorscale="Viridis")
fig = go.Figure(data=[trace],
                layout={'xaxis': {'type': 'category'}})
iplot(fig)

@plotly/plotly_js How does the categorical axis detection algorithm work? Is it getting thrown off because some of these strings contain representations of valid numbers?

[etpinard]

Ha, our auto-type algo must think 3E2 is 300 in exponential notation. Switching those E to e.g. B seems to make things work ok: https://codepen.io/etpinard/pen/oOZeXp?editors=1010

[etpinard]

The full algo is here: https://github.com/plotly/plotly.js/blob/54586b86e09b34aa1a669cdf30e088e36dd32cd0/src/plots/cartesian/axis_autotype.js

[nicolaskruchten]

the operative part of that link above is // require twice as many DISTINCT categories as distinct numbers so basically all the xEy count as distinct numbers and the others as categories.

[gvwilson]

Hi - we are currently trying to tidy up Plotly's public repositories to help us focus our efforts on things that will help users most. Since this issue has been sitting for several years, I'm going to close it. If it's still a concern, we'd be grateful if you could open a new issue (with a short reproducible example if appropriate) so that we can add it to our backlog. Thanks for your help - @gvwilson