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/*
 * #%L
 * Image processing operations for SciJava Ops.
 * %%
 * Copyright (C) 2014 - 2024 SciJava developers.
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 * modification, are permitted provided that the following conditions are met:
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 *    and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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package org.scijava.ops.image.stats;

import net.imglib2.type.numeric.RealType;

import org.scijava.function.Computers;
import org.scijava.ops.spi.Op;

/**
 * Op to calculate the {@code stats.stdDev} directly.
 *
 * @author Daniel Seebacher (University of Konstanz)
 * @author Christian Dietz (University of Konstanz)
 * @param  input type
 * @param  output type
 * @implNote op names='stats.stdDev'
 */
public class IterableStandardDeviation, O extends RealType>
	implements Computers.Arity1, O>
{

	/**
	 * TODO
	 *
	 * @param input
	 * @param stdDev
	 */
	@Override
	public void compute(final Iterable input, final O stdDev) {
		double sum = 0;
		double sumSqr = 0;
		int n = 0;

		for (final I in : input) {
			final double px = in.getRealDouble();
			++n;
			sum += px;
			sumSqr += px * px;
		}

		stdDev.setReal(Math.sqrt((sumSqr - sum * sum / n) / (n - 1)));
	}

}