ggplot hist draft fix (#711)

CHANGELOG.md

@@ -3,6 +3,8 @@
 ## 0.8.1dev
 * [Fix] Fix error that was incorrectly converted into a print message
 
+* [Fix] Fixed vertical color breaks in histograms (#702)
+
 ## 0.8.0 (2023-07-18)
 
 * [Feature] Modified `TableDescription` to add styling, generate messages and format the calculated outputs ([#459](https://github.com/ploomber/jupysql/issues/459))

doc/user-guide/ggplot.md

@@ -5,7 +5,7 @@ jupytext:
     extension: .md
     format_name: myst
     format_version: 0.13
-    jupytext_version: 1.14.5
+    jupytext_version: 1.14.7
 kernelspec:
   display_name: Python 3 (ipykernel)
   language: python
@@ -185,6 +185,12 @@ We can show a histogram of multiple columns by setting `x=['cut', 'color']`
 (ggplot("diamonds", aes(x=["cut", "color"])) + geom_histogram())
 ```
 
+We can also plot histograms for a combination of categorical and numerical columns.
+
+```{code-cell} ipython3
+(ggplot("diamonds", aes(x=["color", "carat"])) + geom_histogram(bins=30))
+```
+
 Apply a custom color with `color` and `fill`
 
 ```{code-cell} ipython3

src/sql/plot.py

@@ -306,14 +306,30 @@ def _are_numeric_values(*values):
     return all([isinstance(value, (int, float)) for value in values])
 
 
-def _get_bar_width(ax, bins):
+def _get_bar_width(ax, bins, bin_size):
     """
     Return a single bar width based on number of bins
     If bins values are str, calculate value based on figure size.
+
+    Parameters
+    ----------
+    ax : matplotlib.Axes
+        Generated plot
+
+    bins : tuple
+        Contains bins' midpoints as float
+
+    bin_size : int or None
+        Calculated bin_size from the _histogram function
+
+    Returns
+    -------
+    width : float
+        A single bar width
     """
 
-    if _are_numeric_values(bins[-1], bins[-2]):
-        width = bins[-1] - bins[-2]
+    if _are_numeric_values(bin_size):
+        width = bin_size
     else:
         fig = plt.gcf()
         bbox = ax.get_window_extent()
@@ -398,7 +414,7 @@ def histogram(
             raise ValueError("Column name has not been specified")
 
         bin_, height, bin_size = _histogram(table, column, bins, with_=with_, conn=conn)
-        width = _get_bar_width(ax, bin_)
+        width = _get_bar_width(ax, bin_, bin_size)
         data = _histogram_stacked(
             table, column, category, bin_, bin_size, with_=with_, conn=conn, facet=facet
         )
@@ -441,10 +457,10 @@ def histogram(
         ax.set_title(f"Histogram from {table!r}")
         ax.legend()
     elif isinstance(column, str):
-        bin_, height, _ = _histogram(
+        bin_, height, bin_size = _histogram(
             table, column, bins, with_=with_, conn=conn, facet=facet
         )
-        width = _get_bar_width(ax, bin_)
+        width = _get_bar_width(ax, bin_, bin_size)
 
         ax.bar(
             bin_,
@@ -460,10 +476,10 @@ def histogram(
 
     else:
         for i, col in enumerate(column):
-            bin_, height, _ = _histogram(
+            bin_, height, bin_size = _histogram(
                 table, col, bins, with_=with_, conn=conn, facet=facet
             )
-            width = _get_bar_width(ax, bin_)
+            width = _get_bar_width(ax, bin_, bin_size)
 
             if isinstance(color, list):
                 color_ = color[i]