Improve MultiLabelConfusionMatrix.toString (#136)

* more readable MultiLabelConfusionMatrix.toString

* include label for which there are no predictions in ConfusionMetrics.accuracy log message

Author: nezda

Classification/Core/src/main/java/org/tribuo/classification/evaluation/ConfusionMetrics.java

@@ -60,7 +60,7 @@ public static <T extends Classifiable<T>> double accuracy(T label, ConfusionMatr
         double support = cm.support(label);
         // handle div-by-zero
         if (support == 0d) {
-            logger.warning("No predictions: accuracy ill-defined");
+            logger.warning("No predictions for " + label + ": accuracy ill-defined");
             return Double.NaN;
         }
         return cm.tp(label) / cm.support(label);

MultiLabel/Core/src/main/java/org/tribuo/multilabel/evaluation/MultiLabelConfusionMatrix.java

@@ -28,6 +28,7 @@
 import java.util.List;
 import java.util.Set;
 import java.util.function.Function;
+import java.util.stream.Collectors;
 
 /**
  * A {@link ConfusionMatrix} which accepts {@link MultiLabel}s.
@@ -158,15 +159,18 @@ public double confusion(MultiLabel predicted, MultiLabel truth) {
 
     @Override
     public String toString() {
-        StringBuilder sb = new StringBuilder();
-        sb.append("[");
-        for (int i = 0; i < mcm.length; i++) {
-            DenseMatrix cm = mcm[i];
-            sb.append(cm.toString());
-            sb.append("\n");
-        }
-        sb.append("]");
-        return sb.toString();
+        return getDomain().getDomain().stream()
+            .map(multiLabel -> {
+                  final int tp = (int) tp(multiLabel);
+                  final int fn = (int) fn(multiLabel);
+                  final int fp = (int) fp(multiLabel);
+                  final int tn = (int) tn(multiLabel);
+                  return String.join("\n",
+                      multiLabel.toString(),
+                      String.format("    [tn: %,d fn: %,d]", tn, fn),
+                      String.format("    [fp: %,d tp: %,d]", fp, tp));
+                }
+            ).collect(Collectors.joining("\n"));
     }
 
     static ConfusionMatrixTuple tabulate(ImmutableOutputInfo<MultiLabel> domain, List<Prediction<MultiLabel>> predictions) {