src/lib/numObscure.c 1.1

Index: src/lib/numObscure.c
===================================================================
RCS file: src/lib/numObscure.c
diff -N src/lib/numObscure.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ src/lib/numObscure.c	25 Nov 2009 17:52:55 -0000	1.1
@@ -0,0 +1,65 @@
+/* numObscure - obscure but sometimes useful numerical functions. */
+#include "common.h"
+#include "obscure.h"
+
+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 < 12)
+    increment = 1;
+else if (scaledSize < 20)
+    increment = 2;
+else if (scaledSize < 75)
+    increment = 5;
+else
+    increment = 10;
+increment *= exponent;
+
+int startInIncrements = floor(start/increment);
+int endInIncrements = ceil(end/increment);
+*retStart = startInIncrements * increment;
+*retEnd = endInIncrements * increment;
+}
+