Fix linear model smoothing with weights

Author: has2k1

doc/changelog.qmd

@@ -10,6 +10,10 @@ title: Changelog
 - Added [](:class:`~plotnine.composition.plot_layout`) with which you can customise the
   layout of plots in composition.
 
+### Bug Fixes
+
+- Fixed [](:class:`~plotnine.geom_smooth`) / [](:class:`~plotnine.stat_smooth`) when using a linear model via "lm" with weights for the model to do a weighted regression. This bug did not affect the formula API of the linear model. ({{< issue 1005 >}})
+
 ## v0.15.1
 (2025-09-30)
 

plotnine/stats/smoothers.py

@@ -64,7 +64,7 @@ def lm(data, xseq, params) -> pd.DataFrame:
 
     X = sm.add_constant(data["x"])
     Xseq = sm.add_constant(xseq)
-    weights = data.get("weights", None)
+    weights = data.get("weight", None)
 
     if weights is None:
         init_kwargs, fit_kwargs = separate_method_kwargs(