Added top 25% gene lists.

common.py

@@ -244,6 +244,9 @@ def violin_with_thresh(data, thresh, ylabel,
     """
     Draw a violin plot from *data* with a horizontal line at value *thresh*.
 
+    If *thresh* is a single value, the line will be red.
+    If *thresh* contains pairs, it will be assumed that these
+    are (threshold, colour) pairs, to be used to plot various lines.
     Y-axis will be labeled using *ylabel*.
     """
     if axis is None:
@@ -253,9 +256,14 @@ def violin_with_thresh(data, thresh, ylabel,
     [body] = violin_parts["bodies"]
     body.set_facecolor(facecolor)
     body.set_edgecolor("black")
-    axis.axhline(thresh, color="red")
+    try:
+        (val, col) = thresh[0]
+    except TypeError:
+        thresh = [(thresh, "red")]
+    for (val, col) in thresh:
+        axis.axhline(val, color=col)
         axis.text(
-        1.01, thresh, f"{thresh:.3}",
+            1.01, val, f"{val:.3}",
             horizontalalignment="left", verticalalignment="bottom")
     (q0, q1, median, q3, q4) = np.percentile(  # pylint: disable=C0103
         data, [0, 25, 50, 75, 100])