feat: Added Table.plot_histograms to plot a histogram for each colu…

…mn in the table (#252)

Closes #157.

### Summary of Changes

Added `Table.plot_histograms` to plot a histpogram for each column in
the table
Changed xticks in `Column.plot_histogram` to match
`Table.plot_histograms` (the first and last xtick labels are outside of
the value range)

---------

Co-authored-by: sibre28 <[email protected]>
Co-authored-by: Lars Reimann <[email protected]>

docs/tutorials/data_visualization.ipynb

@@ -210,6 +210,26 @@
     }
    }
   },
+  {
+   "cell_type": "markdown",
+   "source": [
+    "## Histogram of all columns"
+   ],
+   "metadata": {
+    "collapsed": false
+   }
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "outputs": [],
+   "source": [
+    "titanic_numerical.plot_histograms()"
+   ],
+   "metadata": {
+    "collapsed": false
+   }
+  },
   {
    "cell_type": "markdown",
    "source": [

src/safeds/data/tabular/containers/_table.py

@@ -1313,6 +1313,35 @@ def plot_scatterplot(self, x_column_name: str, y_column_name: str) -> Image:
         buffer.seek(0)
         return Image(buffer, format_=ImageFormat.PNG)
 
+    def plot_histograms(self) -> Image:
+        """
+        Plot a histogram for every column.
+
+        Returns
+        -------
+        plot: Image
+            The plot as an image.
+        """
+        col_wrap = min(self.number_of_columns, 3)
+
+        data = pd.melt(self._data, value_vars=self.column_names)
+        grid = sns.FacetGrid(data=data, col="variable", col_wrap=col_wrap, sharex=False, sharey=False)
+        grid.map(sns.histplot, "value")
+        grid.set_xlabels("")
+        grid.set_ylabels("")
+        grid.set_titles("{col_name}")
+        for axes in grid.axes.flat:
+            axes.set_xticks(axes.get_xticks())
+            axes.set_xticklabels(axes.get_xticklabels(), rotation=45, horizontalalignment="right")
+        grid.tight_layout()
+        fig = grid.fig
+
+        buffer = io.BytesIO()
+        fig.savefig(buffer, format="png")
+        plt.close()
+        buffer.seek(0)
+        return Image(buffer, ImageFormat.PNG)
+
     # ------------------------------------------------------------------------------------------------------------------
     # Conversion
     # ------------------------------------------------------------------------------------------------------------------

tests/safeds/data/tabular/containers/_column/test_plot_boxplot.py

@@ -11,7 +11,10 @@ def test_should_match_snapshot() -> None:
     table.get_column("A").plot_boxplot()
     current = table.get_column("A").plot_boxplot()
     snapshot = Image.from_png_file(resolve_resource_path("./image/snapshot_boxplot.png"))
-    assert snapshot._image.tobytes() == current._image.tobytes()
+
+    # Inlining the expression into the assert causes pytest to hang if the assertion fails when run from PyCharm.
+    assertion = snapshot._image.tobytes() == current._image.tobytes()
+    assert assertion
 
 
 def test_should_raise_if_column_contains_non_numerical_values() -> None:

tests/safeds/data/tabular/containers/_column/test_plot_histogram.py

@@ -8,7 +8,10 @@ def test_should_match_snapshot_numeric() -> None:
     table = Table({"A": [1, 2, 3]})
     current = table.get_column("A").plot_histogram()
     snapshot = Image.from_png_file(resolve_resource_path("./image/snapshot_histogram_numeric.png"))
-    assert snapshot._image.tobytes() == current._image.tobytes()
+
+    # Inlining the expression into the assert causes pytest to hang if the assertion fails when run from PyCharm.
+    assertion = snapshot._image.tobytes() == current._image.tobytes()
+    assert assertion
 
 
 def test_should_match_snapshot_str() -> None:

tests/safeds/data/tabular/containers/_table/test_plot_correlation_heatmap.py

@@ -7,5 +7,8 @@
 def test_should_match_snapshot() -> None:
     table = Table({"A": [1, 2, 3.5], "B": [0.2, 4, 77]})
     current = table.plot_correlation_heatmap()
-    legacy = Image.from_png_file(resolve_resource_path("./image/snapshot_heatmap.png"))
-    assert legacy._image.tobytes() == current._image.tobytes()
+    snapshot = Image.from_png_file(resolve_resource_path("./image/snapshot_heatmap.png"))
+
+    # Inlining the expression into the assert causes pytest to hang if the assertion fails when run from PyCharm.
+    assertion = snapshot._image.tobytes() == current._image.tobytes()
+    assert assertion

tests/safeds/data/tabular/containers/_table/test_plot_histograms.py

@@ -0,0 +1,24 @@
+import pytest
+from safeds.data.image.containers import Image
+from safeds.data.tabular.containers import Table
+
+from tests.helpers import resolve_resource_path
+
+
+@pytest.mark.parametrize(
+    ("table", "path"),
+    [
+        (Table({"A": [1, 2, 3]}), "./image/snapshot_histograms/one_column.png"),
+        (
+            Table({"A": [1, 2, 3], "B": ["A", "A", "Bla"], "C": [True, True, False], "D": [1.0, 2.1, 4.5]}),
+            "./image/snapshot_histograms/four_columns.png",
+        ),
+    ],
+)
+def test_should_match_snapshot(table: Table, path: str) -> None:
+    current = table.plot_histograms()
+    snapshot = Image.from_png_file(resolve_resource_path(path))
+
+    # Inlining the expression into the assert causes pytest to hang if the assertion fails when run from PyCharm.
+    assertion = snapshot._image.tobytes() == current._image.tobytes()
+    assert assertion

tests/safeds/data/tabular/containers/_table/test_plot_lineplot.py

@@ -10,7 +10,10 @@ def test_should_match_snapshot() -> None:
     table = Table({"A": [1, 2, 3], "B": [2, 4, 7]})
     current = table.plot_lineplot("A", "B")
     snapshot = Image.from_png_file(resolve_resource_path("./image/snapshot_lineplot.png"))
-    assert snapshot._image.tobytes() == current._image.tobytes()
+
+    # Inlining the expression into the assert causes pytest to hang if the assertion fails when run from PyCharm.
+    assertion = snapshot._image.tobytes() == current._image.tobytes()
+    assert assertion
 
 
 @pytest.mark.parametrize(

tests/safeds/data/tabular/containers/_table/test_plot_scatterplot.py

@@ -10,7 +10,10 @@ def test_should_match_snapshot() -> None:
     table = Table({"A": [1, 2, 3], "B": [2, 4, 7]})
     current = table.plot_scatterplot("A", "B")
     snapshot = Image.from_png_file(resolve_resource_path("./image/snapshot_scatterplot.png"))
-    assert snapshot._image.tobytes() == current._image.tobytes()
+
+    # Inlining the expression into the assert causes pytest to hang if the assertion fails when run from PyCharm.
+    assertion = snapshot._image.tobytes() == current._image.tobytes()
+    assert assertion
 
 
 @pytest.mark.parametrize(