Replaced reduce function in table with the use of SummaryFunction

src/main/java/com/github/lwhite1/tablesaw/api/Table.java

@@ -21,7 +21,6 @@
 import com.github.lwhite1.tablesaw.table.Projection;
 import com.github.lwhite1.tablesaw.table.Relation;
 import com.github.lwhite1.tablesaw.table.Rows;
-import com.github.lwhite1.tablesaw.table.ViewGroup;
 import com.github.lwhite1.tablesaw.util.IntComparatorChain;
 import com.github.lwhite1.tablesaw.util.ReversingIntComparator;
 import com.github.lwhite1.tablesaw.util.Selection;
@@ -677,15 +676,9 @@ public static Table readTable(String tableNameAndPath) {
      */
     public double reduce(String numericColumnName, NumericReduceFunction function) {
         Column column = column(numericColumnName);
-
         return function.reduce(column.toDoubleArray());
     }
 
-    public Table reduce(String numericColumnName, NumericReduceFunction function, String... groupColumnName) {
-        ViewGroup tableGroup = ViewGroup.create(this, groupColumnName);
-        return tableGroup.reduce(numericColumnName, function);
-    }
-
     /**
      * Returns a new table constructed from a character delimited (aka CSV) text file
      * <p>

src/main/java/com/github/lwhite1/tablesaw/reducing/functions/SummaryFunction.java

@@ -31,7 +31,7 @@ public Table by(String... columnNames) {
   }
 
   /**
-   * Returns the result of applying to the function once to all the values in the original column
+   * Returns the result of applying to the function to all the values in the appropriate column
    */
   public double get() {
     return original.reduce(summarizedColumnName, function());

src/test/java/com/github/lwhite1/tablesaw/examples/ServiceExample.java

@@ -1,13 +1,11 @@
 package com.github.lwhite1.tablesaw.examples;
 
-import com.github.lwhite1.tablesaw.api.Table;
 import com.github.lwhite1.tablesaw.api.DateTimeColumn;
 import com.github.lwhite1.tablesaw.api.LongColumn;
+import com.github.lwhite1.tablesaw.api.Table;
 import it.unimi.dsi.fastutil.floats.FloatArrayList;
 
-import static com.github.lwhite1.tablesaw.reducing.NumericReduceUtils.median;
-import static com.github.lwhite1.tablesaw.api.QueryHelper.allOf;
-import static com.github.lwhite1.tablesaw.api.QueryHelper.column;
+import static com.github.lwhite1.tablesaw.api.QueryHelper.*;
 
 /**
  * Usage example using a Tornado dataset
@@ -44,7 +42,7 @@ public static void main(String[] args) throws Exception {
               (column("SKU").startsWith("429")),
               (column("Operation").isEqualTo("Assembly"))));
 
-    Table durationByFacilityAndShift = q2_429_assembly.reduce("Duration", median, "Facility", "Shift");
+    Table durationByFacilityAndShift = q2_429_assembly.median("Duration").by("Facility", "Shift");
     // TODO(lwhite): We need a top() method that can be used to return the top table rows
     FloatArrayList tops = durationByFacilityAndShift.floatColumn("Median").top(5);
 

src/test/java/com/github/lwhite1/tablesaw/examples/TornadoExample.java

@@ -1,7 +1,8 @@
 package com.github.lwhite1.tablesaw.examples;
 
-import com.github.lwhite1.tablesaw.reducing.NumericReduceUtils;
-import com.github.lwhite1.tablesaw.api.*;
+import com.github.lwhite1.tablesaw.api.CategoryColumn;
+import com.github.lwhite1.tablesaw.api.ColumnType;
+import com.github.lwhite1.tablesaw.api.Table;
 
 import static com.github.lwhite1.tablesaw.api.ColumnType.*;
 import static com.github.lwhite1.tablesaw.api.QueryHelper.column;
@@ -80,13 +81,13 @@ public static void main(String[] args) throws Exception {
 
 
     //TODO(lwhite): Provide a param for title of the new table (or auto-generate a better one).
-    Table injuriesByScale = tornadoes.reduce("Injuries", NumericReduceUtils.median, "Scale");
+    Table injuriesByScale = tornadoes.median("Injuries").by("Scale");
     injuriesByScale.setName("Median injuries by Tornado Scale");
     out(injuriesByScale.print());
 
 
     //TODO(lwhite): Provide a param for title of the new table (or auto-generate a better one).
-    Table injuriesByScaleState = tornadoes.reduce("Injuries", NumericReduceUtils.median, "Scale", "State");
+    Table injuriesByScaleState = tornadoes.median("Injuries").by("Scale", "State");
     injuriesByScaleState.setName("Median injuries by Tornado Scale and State");
     out(injuriesByScaleState.print());
 

src/test/java/com/github/lwhite1/tablesaw/integration/AirlineDelays2.java

@@ -1,12 +1,12 @@
 package com.github.lwhite1.tablesaw.integration;
 
-import com.github.lwhite1.tablesaw.api.*;
-
+import com.github.lwhite1.tablesaw.api.BooleanColumn;
+import com.github.lwhite1.tablesaw.api.ColumnType;
+import com.github.lwhite1.tablesaw.api.Table;
 import com.google.common.base.Stopwatch;
 
 import java.util.concurrent.TimeUnit;
 
-import static com.github.lwhite1.tablesaw.reducing.NumericReduceUtils.mean;
 import static com.github.lwhite1.tablesaw.api.ColumnType.*;
 import static com.github.lwhite1.tablesaw.api.QueryHelper.*;
 import static java.lang.System.out;
@@ -79,22 +79,22 @@ private AirlineDelays2() throws Exception {
 
     // Compute average number of delayed flights per month
 
-    Table monthGroup = ord.reduce("DepDelay", mean, "Month");
+    Table monthGroup = ord.mean("DepDelay").by("Month");
     out(monthGroup.print());
     //TODO Plot
 
-    Table dayOfWeekGroup = ord.reduce("DepDelay", mean, "DayOfWeek");
+    Table dayOfWeekGroup = ord.mean("DepDelay").by("DayOfWeek");
     out(dayOfWeekGroup.print());
     //TODO Plot
 
     ord.addColumn(ord.timeColumn("CRSDepTime").hour());
     System.out.println(ord.columnNames());
-    Table hourGroup = ord.reduce("DepDelay", mean, "CRSDepTime[hour]");
+    Table hourGroup = ord.mean("DepDelay").by("CRSDepTime[hour]");
     out(hourGroup.print());
     //TODO Plot
 
     // Compute average number of delayed flights per carrier
-    Table carrierGroup = ord.reduce("DepDelay", mean, "UniqueCarrier");
+    Table carrierGroup = ord.mean("DepDelay").by("UniqueCarrier");
     carrierGroup = carrierGroup.sortDescendingOn("Mean");
     out(carrierGroup.print());
   }