Starting work to bring splitting and aggregating up to Outlier levels of functionality

Author: lwhite1

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

@@ -540,7 +540,7 @@ public Table appendText(CategoryColumn sumColumn, CategoryColumn byColumn) {
     return resultTable;
   }
 
-  public Table sum(IntColumn sumColumn, String[] byColumnNames) {
+  public Table sum(IntColumn sumColumn, String... byColumnNames) {
     TableGroup groupTable = new TableGroup(this, byColumnNames);
     Table resultTable = new Table(name + " summary");
 
@@ -556,10 +556,15 @@ public Table sum(IntColumn sumColumn, String[] byColumnNames) {
       groupColumn.add(groupName);
       sumColumn1.add((int) sum);
     }
-
     return resultTable;
   }
 
+/*
+  public Average average(String summarizedColumnName) {
+    return new Average(this, summarizedColumnName);
+  }
+*/
+
   public CategoryColumn categoryColumn(String columnName) {
     return (CategoryColumn) column(columnName);
   }

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

@@ -3,6 +3,7 @@
 import com.github.lwhite1.tablesaw.Table;
 import com.github.lwhite1.tablesaw.api.ColumnType;
 import com.github.lwhite1.tablesaw.columns.CategoryColumn;
+import com.github.lwhite1.tablesaw.columns.IntColumn;
 import com.github.lwhite1.tablesaw.io.CsvReader;
 import com.github.lwhite1.tablesaw.io.CsvWriter;
 import com.github.lwhite1.tablesaw.store.StorageManager;
@@ -78,6 +79,14 @@ public static void main(String[] args) throws Exception {
     out("Calculating basic descriptive statistics on Fatalities");
     out(fatal.intColumn("Fatalities").stats().asTable("").print());
 
+
+    //TODO(lwhite): Provide a param for title of the new table (or auto-generate a better one).
+    IntColumn injuries = tornadoes.intColumn("Injuries");
+    Table sumInjuriesByScale = tornadoes.sum(injuries, "Scale");
+    sumInjuriesByScale.setName("Total injuries by Tornado Scale");
+    out(sumInjuriesByScale.print());
+
+
     out();
     out("Writing the revised table to a new csv file");
     CsvWriter.write("data/rev_tornadoes_1950-2014.csv", tornadoes);