tech.tablesaw.api.CategoricalColumn Maven / Gradle / Ivy
/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package tech.tablesaw.api;
import java.util.Map;
import it.unimi.dsi.fastutil.objects.Object2IntMap;
import it.unimi.dsi.fastutil.objects.Object2IntOpenHashMap;
import tech.tablesaw.columns.Column;
/**
* A column type that can be summarized, or serve as a grouping variable in cross tabs or other aggregation operations.
*
* The column data is generally discrete, however NumberColumn implements CategoricalColumn so that it can be used to
* summarize when it contains ints. If you use it to summarize over a large range of floating point numbers, you
* will likely run out of memory.
*
* Supporting subtypes include:
* - StringColumn
* - BooleanColumn
* - DateColumn,
* - etc
*
* DateTimeColumn is not included. TimeColumn can be converted to ints without loss of data, so it does implement this
* interface
*/
public interface CategoricalColumn extends Column {
default Table countByCategory() {
final Table t = new Table("Column: " + name());
final CategoricalColumn categories = (CategoricalColumn) type().create("Category");
final IntColumn counts = IntColumn.create("Count");
final Object2IntMap valueToCount = new Object2IntOpenHashMap<>();
for (int i = 0; i < size(); i++) {
final String next = getString(i);
if (valueToCount.containsKey(next)) {
valueToCount.put(next, valueToCount.getInt(next) + 1);
} else {
valueToCount.put(next, 1);
}
}
for (Map.Entry entry : valueToCount.object2IntEntrySet()) {
categories.appendCell(entry.getKey());
counts.append(entry.getValue());
}
if (countMissing() > 0) {
categories.appendMissing();
counts.append(countMissing());
}
t.addColumns(categories);
t.addColumns(counts);
return t;
}
}