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Tensorics is a java framework which uses a tensor as a central object. A tensor represents a set of values placed in an N-dimensional space. Wherever you are tempted to use maps of maps, a tensor might be a good choice ;-) Tensorics provides methods to create, transform and performing calculations with those tensors.

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 * This file is part of tensorics.
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 * Copyright (c) 2008-2011, CERN. All rights reserved.
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 * 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
 *
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// @formatter:on

package org.tensorics.core.iterable.operations;

import static com.google.common.collect.Iterables.isEmpty;

import org.tensorics.core.math.ExtendedField;
import org.tensorics.core.scalar.lang.ScalarSupport;

/**
 * An operation that takes and iterable of a certain type of values (for which a field has to be provided) and
 * calculates the rms (Root mean square) out of it.
 * 
 * For the definition of the root mean square, have a look at wikipedia.
 * 
 * @author kfuchsbe
 * @param  the type of the scalars (elements of the field on which the rms will be based)
 */
public class IterableRms extends ScalarSupport implements IterableOperation {

    private final IterableSumOfSquares sumOfSquares;
    private final IterableSize size;

    public IterableRms(ExtendedField field) {
        super(field);
        this.sumOfSquares = new IterableSumOfSquares<>(field);
        this.size = new IterableSize<>(field);
    }

    @Override
    public V apply(Iterable values) {
        if (isEmpty(values)) {
            throw new IllegalArgumentException("r.m.s. of empty value set is not possible.");
        }
        return squareRootOf(calculate(sumOfSquares.apply(values)).dividedBy(size.apply(values)));

    }

}