gh.plot_hypothesis1 error in windows python conda

[cesar-moya]

First off, thank you for such an an amazing book. I am experiencing this issue where some plots (not all) throw the below error in a windows environment using conda. Not sure if it's a bug or an issue on my side, if possible please let me know:

File: 01-g-h-filter.ipynb
Cell: 8

import kf_book.gh_internal as gh
gh.plot_hypothesis1()

Error:

c:\Kalman-and-Bayesian-Filters-in-Python\kf_book\gh_internal.py:140: SyntaxWarning: invalid escape sequence '\h'
  plt.text (0.0, 159.8, "last estimate ($\hat{x}_{t-1}$)", ha='left', va='top',fontsize=18)

Thanks,

[fnndyl]

I am also having this issue, may be something to do with an update since this was written 3/4 years ago in matplotlib? But I am not an expert.

[cm-1]

It looks like a change happened in a recent version of Python. When I run x = "last estimate ($\hat{x}_{t-1}$)" in a Python 3.11 environment, everything's fine, while in 3.13, I get the SyntaxWarning (and I haven't tested 3.12 or looked through release info to see what's changed).

In any event, the fix is easy. Just go into gh_internal.py and put an r in front of the offending strings to make them raw strings.