give Lib.findBin a tiny buffer for on-the-line points

Author: alexcjohnson

src/lib/search.js

@@ -12,6 +12,11 @@
 var isNumeric = require('fast-isnumeric');
 var loggers = require('./loggers');
 
+// don't trust floating point equality - fraction of bin size to call
+// "on the line" and ensure that they go the right way specified by
+// linelow
+var roundingError = 1e-9;
+
 
 /**
  * findBin - find the bin for val - note that it can return outside the
@@ -26,20 +31,21 @@ var loggers = require('./loggers');
 exports.findBin = function(val, bins, linelow) {
     if(isNumeric(bins.start)) {
         return linelow ?
-            Math.ceil((val - bins.start) / bins.size) - 1 :
-            Math.floor((val - bins.start) / bins.size);
+            Math.ceil((val - bins.start) / bins.size - roundingError) - 1 :
+            Math.floor((val - bins.start) / bins.size + roundingError);
     }
     else {
-        var n1 = 0,
-            n2 = bins.length,
-            c = 0,
-            n,
-            test;
-        if(bins[bins.length - 1] >= bins[0]) {
+        var n1 = 0;
+        var n2 = bins.length;
+        var c = 0;
+        var binSize = (n2 > 1) ? (bins[n2 - 1] - bins[0]) / (n2 - 1) : 1;
+        var n, test;
+        if(binSize >= 0) {
             test = linelow ? lessThan : lessOrEqual;
         } else {
             test = linelow ? greaterOrEqual : greaterThan;
         }
+        val += binSize * roundingError * (linelow ? -1 : 1) * (binSize >= 0 ? 1 : -1);
         // c is just to avoid infinite loops if there's an error
         while(n1 < n2 && c++ < 100) {
             n = Math.floor((n1 + n2) / 2);

test/jasmine/tests/histogram_test.js

@@ -423,7 +423,7 @@ describe('Test histogram', function() {
             var trace4 = {x: [1, 1.2, 1.4, 1.6], yaxis: 'y2'};
 
             expect(calcPositions(trace1, [trace2, trace3, trace4])).toEqual([1, 2, 3, 4]);
-            expect(calcPositions(trace3)).toBeCloseToArray([0.9, 1.1, 1.3], 5);
+            expect(calcPositions(trace3)).toBeCloseToArray([1.1, 1.3], 5);
         });
 
         describe('cumulative distribution functions', function() {