Merge pull request #210 from domoritz/fix-nice

Ensure that niced domains always span ticks

Author: Fil

src/linear.js

@@ -19,38 +19,36 @@ export function linearish(scale) {
   scale.nice = function(count) {
     if (count == null) count = 10;
 
-    var d = domain(),
-        i0 = 0,
-        i1 = d.length - 1,
-        start = d[i0],
-        stop = d[i1],
-        step;
+    var d = domain();
+    var i0 = 0;
+    var i1 = d.length - 1;
+    var start = d[i0];
+    var stop = d[i1];
+    var prestep;
+    var step;
+    var maxIter = 10;
 
     if (stop < start) {
       step = start, start = stop, stop = step;
       step = i0, i0 = i1, i1 = step;
     }
-
-    step = tickIncrement(start, stop, count);
-
-    if (step > 0) {
-      start = Math.floor(start / step) * step;
-      stop = Math.ceil(stop / step) * step;
+    
+    while (maxIter-- > 0) {
       step = tickIncrement(start, stop, count);
-    } else if (step < 0) {
-      start = Math.ceil(start * step) / step;
-      stop = Math.floor(stop * step) / step;
-      step = tickIncrement(start, stop, count);
-    }
-
-    if (step > 0) {
-      d[i0] = Math.floor(start / step) * step;
-      d[i1] = Math.ceil(stop / step) * step;
-      domain(d);
-    } else if (step < 0) {
-      d[i0] = Math.ceil(start * step) / step;
-      d[i1] = Math.floor(stop * step) / step;
-      domain(d);
+      if (step === prestep) {
+        d[i0] = start
+        d[i1] = stop
+        return domain(d);
+      } else if (step > 0) {
+        start = Math.floor(start / step) * step;
+        stop = Math.ceil(stop / step) * step;
+      } else if (step < 0) {
+        start = Math.ceil(start * step) / step;
+        stop = Math.floor(stop * step) / step;
+      } else {
+        break;
+      }
+      prestep = step;
     }
 
     return scale;

test/linear-test.js

@@ -373,6 +373,36 @@ tape("linear.ticks(count) returns the expected ticks for a polylinear domain", f
   test.end();
 });
 
+tape("linear.ticks(X) spans linear.nice(X).domain()", function(test) {
+  function check(domain, count) {
+    var s = scale.scaleLinear().domain(domain).nice(count);
+    var ticks = s.ticks(count);
+    test.deepEqual([ticks[0], ticks[ticks.length - 1]], s.domain());
+  }
+  
+  check([1, 9], 2);
+  check([1, 9], 3);
+  check([1, 9], 4);
+
+  check([8, 9], 2);
+  check([8, 9], 3);
+  check([8, 9], 4);
+
+  check([1, 21], 2);
+  check([2, 21], 2);
+  check([3, 21], 2);
+  check([4, 21], 2);
+  check([5, 21], 2);
+  check([6, 21], 2);
+  check([7, 21], 2);
+  check([8, 21], 2);
+  check([9, 21], 2);
+  check([10, 21], 2);
+  check([11, 21], 2);
+
+  test.end();
+})
+
 tape("linear.ticks(count) returns the empty array if count is not a positive integer", function(test) {
   var s = scale.scaleLinear();
   test.deepEqual(s.ticks(NaN), []);