Merge pull request #22 from metamx/histograms

HistogramVisual: add support for quantiles

common/src/main/java/com/metamx/druid/aggregation/Histogram.java

@@ -132,10 +132,15 @@ public class Histogram
     return buf.array();
   }
 
+  /**
+   * Returns a visual representation of a histogram object.
+   * Initially returns an array of just the min. and max. values
+   * but can also support the addition of quantiles.
+   */
   public HistogramVisual asVisual() {
     float[] visualCounts = new float[bins.length - 2];
     for(int i = 0; i < visualCounts.length; ++i) visualCounts[i] = (float)bins[i + 1];
-    return new HistogramVisual(breaks, visualCounts, min, max);
+    return new HistogramVisual(breaks, visualCounts, new float[]{min, max});
   }
 
   public static Histogram fromBytes(byte[] bytes) {

common/src/main/java/com/metamx/druid/aggregation/HistogramVisual.java

@@ -29,15 +29,14 @@ public class HistogramVisual
 {
   @JsonProperty final public double[] breaks;
   @JsonProperty final public double[] counts;
-  @JsonProperty final double min;
-  @JsonProperty final double max;
+  // an array of the quantiles including the min. and max.
+  @JsonProperty final public double[] quantiles;
 
   @JsonCreator
   public HistogramVisual(
       @JsonProperty double[] breaks,
       @JsonProperty double[] counts,
-      @JsonProperty double min,
-      @JsonProperty double max
+      @JsonProperty double[] quantiles
   )
   {
     Preconditions.checkArgument(breaks != null, "breaks must not be null");
@@ -46,15 +45,13 @@ public class HistogramVisual
 
     this.breaks = breaks;
     this.counts = counts;
-    this.min = min;
-    this.max = max;
+    this.quantiles = quantiles;
   }
 
   public HistogramVisual(
         float[] breaks,
         float[] counts,
-        float min,
-        float max
+        float[] quantiles
   )
   {
     Preconditions.checkArgument(breaks != null, "breaks must not be null");
@@ -63,10 +60,10 @@ public class HistogramVisual
 
     this.breaks = new double[breaks.length];
     this.counts = new double[counts.length];
+    this.quantiles = new double[quantiles.length];
     for(int i = 0; i < breaks.length; ++i) this.breaks[i] = breaks[i];
     for(int i = 0; i < counts.length; ++i) this.counts[i] = counts[i];
-    this.min = min;
-    this.max = max;
+    for(int i = 0; i < quantiles.length; ++i) this.quantiles[i] = quantiles[i];
   }
 
   @Override
@@ -75,8 +72,7 @@ public class HistogramVisual
     return "HistogramVisual{" +
            "counts=" + Arrays.toString(counts) +
            ", breaks=" + Arrays.toString(breaks) +
-           ", min=" + min +
-           ", max=" + max +
+           ", quantiles=" + Arrays.toString(quantiles) +
            '}';
   }
 }

common/src/test/java/com/metamx/druid/histogram/HistogramTest.java

@@ -68,8 +68,7 @@ public class HistogramTest
     Map<String,Object> expectedObj = Maps.newLinkedHashMap();
     expectedObj.put("breaks", Arrays.asList(visualBreaks));
     expectedObj.put("counts", Arrays.asList(visualCounts));
-    expectedObj.put("min", -1.0);
-    expectedObj.put("max", 1.0);
+    expectedObj.put("quantiles", Arrays.asList(new Double[]{-1.0, 1.0}));
 
     Map<String,Object> obj = (Map<String, Object>)objectMapper.readValue(json, Object.class);
     Assert.assertEquals(expectedObj, obj);