fix: fixed clipping of kde for censored values in violinplot (#38)

src/hydrodiy/plot/tests/test_hyplot_violinplot.py

@@ -132,6 +132,18 @@ def test_violin_missing():
     fig.savefig(fp)
 
 
+def test_violin_censored():
+    plt.close("all")
+    df = DATA1.copy()
+    df.data2 = df.data2.clip(-np.inf, df.data2.quantile(0.3))
+    df.data3 = df.data3.clip(df.data3.quantile(0.3))
+    vl = Violin(data=df)
+    fig, ax = plt.subplots()
+    vl.draw(ax=ax)
+    fp = FIMG / "violin_censored.png"
+    fig.savefig(fp)
+
+
 def test_violin_allnan():
     plt.close("all")
     df = DATA1.copy()

src/hydrodiy/plot/violinplot.py

@@ -219,10 +219,28 @@ def _compute(self):
                 continue
 
             sen = se[notnull]
-            kernel = gaussian_kde(sen.values)
+            values = sen.values
+            x0, x1 = sen.min(), sen.max()
+
+            # reduce impact of censored data
+            ilow = np.abs(values-x0) < 1e-10
+            if ilow.sum() > 1:
+                idx = np.where(ilow)[0][1:]
+                ilow[idx] = False
+
+            ihigh = np.abs(values-x1) < 1e-10
+            if ihigh.sum() > 1:
+                idx = np.where(ihigh)[0][1:]
+                ihigh[idx] = False
+
+            irest = ~ilow & ~ihigh
+
+            selected = irest | ilow | ihigh
+
+            # Run kde estimate
+            kernel = gaussian_kde(values[selected])
 
             # blend regular spacing and ecdf spacing
-            x0, x1 = sen.min(), sen.max()
             x = np.linspace(x0, x1, (npts-len(sen)))
             err = 1e-6*np.random.uniform(-1, 1, len(sen))
             x = np.sort(np.concatenate([x, sen.values+err]))