/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.tajo.engine.function.builtin;
import org.apache.tajo.catalog.Column;
import org.apache.tajo.datum.Datum;
import org.apache.tajo.datum.DatumFactory;
import org.apache.tajo.datum.NullDatum;
import org.apache.tajo.plan.function.FunctionContext;
public abstract class StdDevSamp extends Variance {
public StdDevSamp(Column[] definedArgs) {
super(definedArgs);
}
@Override
public Datum terminate(FunctionContext ctx) {
VarianceContext varianceCtx = (VarianceContext) ctx;
if (varianceCtx.count <= 1) {
return NullDatum.get();
}
return DatumFactory.createFloat8(Math.sqrt(varianceCtx.squareSumOfDiff / (varianceCtx.count - 1)));
}
}