src/lib/obscure.c 1.49

Index: src/lib/obscure.c
===================================================================
RCS file: /projects/compbio/cvsroot/kent/src/lib/obscure.c,v
retrieving revision 1.48
retrieving revision 1.49
diff -b -B -U 4 -r1.48 -r1.49
--- src/lib/obscure.c	23 Sep 2009 18:42:28 -0000	1.48
+++ src/lib/obscure.c	24 Nov 2009 00:59:18 -0000	1.49
@@ -658,4 +658,63 @@
     ++s;
     }
 }
 
+void rangeRoundUp(double start, double end, double *retStart, double *retEnd)
+/* Round start and end so that they cover a slightly bigger range, but with more round
+ * numbers.  For instance 0.23:9.89 becomes 0:10 */
+{
+double size = end - start;
+if (size < 0)
+    errAbort("start (%g) after end (%g) in rangeRoundUp", start, end);
+
+/* Flat ranges get moved to include zero for scale. */
+if (size == 0.0)
+    {
+    if (start < 0.0)
+        {
+	*retStart = start;
+	*retEnd = 0;
+	}
+    else if (start > 0.0)
+        {
+	*retStart = 0;
+	*retEnd = end;
+	}
+    else
+        {
+	*retStart = 0;
+	*retEnd = 1;
+	}
+    return;
+    }
+
+/* Figure out "increment", which will be 1, 2, 5, or 10, or a multiple of 10 of these 
+ * Want to have at least two increments in range. */
+double exponent = 1;
+double scaledSize = size;
+double increment = 0;
+while (scaledSize < 100)
+    {
+    scaledSize *= 10;
+    exponent /= 10;
+    }
+while (scaledSize >= 100)
+    {
+    scaledSize /= 10;
+    exponent *= 10;
+    }
+/* At this point have a number between 10 and 100 */
+if (scaledSize < 10)
+    increment = 1;
+else if (scaledSize < 20)
+    increment = 2;
+else 
+    increment = 5;
+increment *= exponent;
+
+int startInIncrements = floor(start/increment);
+int endInIncrements = ceil(end/increment);
+*retStart = startInIncrements * increment;
+*retEnd = endInIncrements * increment;
+}
+