org.tensorics.core.iterable.operations.IterableStd Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of tensorics-core Show documentation

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.

There is a newer version: 0.0.81

Show newest version

/**
 * Copyright (c) 2016 European Organisation for Nuclear Research (CERN), All Rights Reserved.
 */

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 standard deviation out of it.
 * 
 * For the definition of the standard deviation, have a look at
 * wikipedia.
 * 
 * @author caguiler
 * @param  the type of the scalars (elements of the field on which the standard deviation will be based)
 */
public class IterableStd extends ScalarSupport implements IterableOperation {

    private final IterableVar iterableVar;
    private final ExtendedField field;

    public IterableStd(ExtendedField field) {
        super(field);
        this.field = field;
        this.iterableVar = new IterableVar<>(field);
    }

    @Override
    public V apply(Iterable values) {
        if (isEmpty(values)) {
            throw new IllegalArgumentException("standard deviation of empty value set is not possible.");
        }

        return calculate(iterableVar.apply(values)).root(field.two());
    }

}