Panel label (#90)

* add function to set a panel label

* add test for panel label

* redo add panel label (#5)

* define auxiliary `_lim_loc` within `set_panel_label()`

as suggested by @gidden

* remove skipping plotting-tests in Windows

* adding release notes

RELEASE_NOTES.md

@@ -1,6 +1,7 @@
 
 # Next Release
 
+- (#90)[https://github.com/IAMconsortium/pyam/pull/90] Adding a function to `set_panel_label()` as part of the plotting library
 - (#87)[https://github.com/IAMconsortium/pyam/pull/87] Extending `rename()` to work with model and scenario names
 - (#85)[https://github.com/IAMconsortium/pyam/pull/85] Improved functionality for importing metadata and bugfix for filtering for strings if `nan` values exist in metadata
 - (#83)[https://github.com/IAMconsortium/pyam/pull/83] Extending `filter_by_meta()` to work with non-matching indices between `df` and `data

pyam/plotting.py

@@ -583,3 +583,26 @@ def _add_legend(ax, handles, labels, legend):
             MAX_LEGEND_LABELS))
     legend = {} if legend in [True, None] else legend
     ax.legend(handles, labels, **legend)
+
+
+def set_panel_label(label, ax=None, x=0.05, y=0.9):
+    """Add a panel label to the figure/axes, by default in the top-left corner
+
+    Parameters
+    ----------
+    label : str
+        text to be added as panel label
+    ax : matplotlib.Axes, optional
+        panel to which to add the panel label
+    x : number, default 0.05
+        relative location of label to x-axis
+    y : number, default 0.9
+        relative location of label to y-axis
+    """
+    def _lim_loc(lim, loc):
+        return lim[0] + (lim[1] - lim[0]) * loc
+
+    if ax is not None:
+        ax.text(_lim_loc(ax.get_xlim(), x), _lim_loc(ax.get_ylim(), y), label)
+    else:
+        plt.text(_lim_loc(plt.xlim(), x), _lim_loc(plt.ylim(), y), label)

tests/test_plotting.py

@@ -370,3 +370,10 @@ def test_stack_plot_other(plot_df):
          .stack_plot(ax=ax, stack='scenario', cmap='viridis', title='foo')
          )
     return fig
+
+
+@pytest.mark.mpl_image_compare(**MPL_KWARGS)
+def test_add_panel_label(plot_df):
+    fig, ax = plt.subplots(figsize=(8, 8))
+    plotting.set_panel_label('test', ax=ax, x=0.5, y=0.5)
+    return fig