plot_lm doesn't work with y_model and multidimensional y

[colehaus]

Describe the bug
When the y_model argument to plot_lm is used with multidimensional y, an exception is thrown instead of the appropriate plots being generated.

To Reproduce

See this notebook: https://gist.github.com/colehaus/b2aa195687f53ef7c86eec2ebb3798c2

Expected behavior
I expected a collection of plots to be generated just like happens with plot_dim ordinarily, but there should also be the model info in the plot as happens when a single-dimensional plot is created.

Additional context
Arviz version is 0.11.4.

[ayashabbar]

Hello @colehaus
I would like to contribute to this issue. Are there any updated output you came across?
Thanks in advance,
A. Shabbar

[colehaus]

Hi, thanks for looking at it. I haven't looked into the issue at all since opening it. So the notebook is still the most up-to-date reflection of the situation.

[itsdivya1309]

Hii, has the issue been resolved? If not, I would like to work on this issue.

[uzairgheewala]

Hi @colehaus hope all is well.

I've submitted PR #2408 that fixes the dimension handling issues with plot_lm when using y_model with multidimensional data.
The PR addresses both failure cases mentioned in your notebook and introduces a test to prevent any regressions.

For lines mode: Fixed sample indexing and dimension handling to properly maintain the relationship between samples and x-points
For HDI mode: Corrected the data reshape operations to ensure samples are properly aligned.

Please let me know if there are any further issues.