Example usage for java.lang Math log

Introduction

In this page you can find the example usage for java.lang Math log.

Prototype

@HotSpotIntrinsicCandidate
public static double log(double a)

Source Link

Document

Returns the natural logarithm (base e) of a double value.

Usage

From source file:beast.math.distribution.GammaDistributionTest.java

/**
 * This test stochastically draws gamma//from  ww w  .  j a va2s  .  co  m
 * variates and compares the coded pdf 
 * with the actual pdf.  
 * The tolerance is required to be at most 1e-10.
 */

static double mypdf(double value, double shape, double scale) {
    return Math.exp(
            (shape - 1) * Math.log(value) - value / scale - Gamma.logGamma(shape) - shape * Math.log(scale));
}

From source file:Main.java

/**
 * See: http://stackoverflow.com/questions/477572/android-strange
 *       -out-of-memory-issue-while-loading-an-image
 *       -to-a-bitmap-object/823966#823966
 * Thanks to StackOverflow user named Fedor.
 *//*  w  ww .  j ava 2 s  . c  o  m*/
public static Bitmap decodeFile(File f, int size) {
    Bitmap b = null;
    try {
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;

        FileInputStream fis = new FileInputStream(f);
        BitmapFactory.decodeStream(fis, null, o);
        fis.close();

        int scale = 1;
        if (o.outHeight > size || o.outWidth > size) {
            scale = (int) Math.pow(2.0, (int) Math
                    .round(Math.log(size / (double) Math.max(o.outHeight, o.outWidth)) / Math.log(0.5)));
        }

        // Decode with inSampleSize
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inTempStorage = new byte[32 * 1024];
        o2.inPurgeable = true;
        o2.inSampleSize = scale;
        fis = new FileInputStream(f);
        b = BitmapFactory.decodeStream(fis, null, o2);
        fis.close();
    } catch (IOException e) {
    }
    return b;
}

From source file:com.opengamma.strata.math.impl.function.special.GammaFunctionTest.java

@Test
public void test() {
    final double x = RANDOM.nextDouble();
    assertEquals(Math.log(GAMMA.applyAsDouble(x)), LN_GAMMA.apply(x), EPS);
}

From source file:gedi.util.math.stat.distributions.LfcDistribution.java

public static double var(double a, double b) {
    return (Gamma.trigamma(a) + Gamma.trigamma(b)) / Math.log(2) / Math.log(2);
}

From source file:gov.nih.nci.calims2.business.inventory.container.CoordinateHelper.java

private static String convertValue(char firstCharacter, int maximum, int value) {
    int length = (int) Math.floor(Math.log(maximum) / Math.log(LETTER_BASE)) + 1;
    if (value == 0) {
        return StringUtils.repeat(Character.toString(firstCharacter), length);
    }//from   w ww  .  j a  v a2 s .com
    String result = "";
    int remaining = value;
    while (remaining > 0) {
        result = Character.toString((char) (firstCharacter + remaining % LETTER_BASE)) + result;
        remaining /= LETTER_BASE;
    }
    while (result.length() < length) {
        result = firstCharacter + result;
    }
    return result;
}

From source file:Main.java

/**
 * Returns the closest power-of-two number less than or equal to x.
 *
 * @param x input value/*from  w w w.  j  av a  2s  . c  o  m*/
 *
 * @return the closest power-of-two number less then or equal to x
 */
public static int prevPow2(int x) {
    if (x < 1) {
        throw new IllegalArgumentException("x must be greater or equal 1");
    }
    return (int) Math.pow(2, Math.floor(Math.log(x) / Math.log(2)));
}

From source file:com.opengamma.analytics.financial.model.option.pricing.tree.LeisenReimerLatticeSpecification.java

@Override
public double[] getParameters(final double spot, final double strike, final double timeToExpiry,
        final double volatility, final double interestRate, final int nSteps, final double dt) {
    Validate.isTrue((nSteps % 2 == 1), "The number of steps should be odd");
    final double sigmaRootT = volatility * Math.sqrt(timeToExpiry);
    final double d1 = (Math.log(spot / strike) + interestRate * timeToExpiry) / sigmaRootT + 0.5 * sigmaRootT;
    final double d2 = d1 - sigmaRootT;
    final double sig1 = d1 >= 0. ? 1. : -1.;
    final double sig2 = d2 >= 0. ? 1. : -1.;
    final double coef1 = d1 / (nSteps + 1. / 3. + 0.1 / (nSteps + 1.));
    final double coef2 = d2 / (nSteps + 1. / 3. + 0.1 / (nSteps + 1.));
    final double p1 = 0.5 + sig1 * 0.5 * Math.sqrt(1. - Math.exp(-coef1 * coef1 * (nSteps + 1. / 6.)));
    final double p2 = 0.5 + sig2 * 0.5 * Math.sqrt(1. - Math.exp(-coef2 * coef2 * (nSteps + 1. / 6.)));
    final double rr = Math.exp(interestRate * dt);
    final double upFactor = rr * p1 / p2;
    final double downFactor = (rr - p2 * upFactor) / (1 - p2);

    return new double[] { upFactor, downFactor, p2, 1 - p2 };
}

From source file:gedi.core.data.reads.functions.ReadDirichletLikelihoodRatioTest.java

public static double logProbability(double[] alpha1, double[] p) {
    double re = 0;
    double asum = 0;
    double gsum = 0;
    for (int i = 0; i < p.length; i++) {
        re += Math.log(p[i]) * (alpha1[i]);
        asum += alpha1[i] + 1;/*from   ww  w . java 2 s  . c om*/
        gsum += Gamma.logGamma(alpha1[i] + 1);
    }
    return re + Gamma.logGamma(asum) - gsum;
}

From source file:Main.java

public static Bitmap loadMpoBitmapFromFile(File file, long offset, int maxWidth, int maxHeight)
        throws IOException {
    // First, decode the width and height of the image, so that we know how much to scale
    // it down when loading it into our ImageView (so we don't need to do a huge allocation).
    BitmapFactory.Options opts = new BitmapFactory.Options();
    InputStream fs = null;/* w w w . j av  a  2s. co m*/
    try {
        fs = new BufferedInputStream(new FileInputStream(file));
        fs.skip(offset);
        opts.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(fs, null, opts);
    } finally {
        if (fs != null) {
            try {
                fs.close();
            } catch (IOException e) {
                // don't worry
            }
        }
    }
    int scale = 1;
    if (opts.outHeight > maxHeight || opts.outWidth > maxWidth) {
        scale = (int) Math.pow(2, (int) Math
                .round(Math.log(maxWidth / (double) Math.max(opts.outHeight, opts.outWidth)) / Math.log(0.5)));
    }
    if ((opts.outHeight <= 0) || (opts.outWidth <= 0)) {
        return null;
    }
    // Decode the image for real, but now with a sampleSize.
    // We have to reopen the file stream, and re-skip to the correct offset, since
    // FileInputStream doesn't support reset().
    Bitmap bmp = null;
    fs = null;
    try {
        fs = new BufferedInputStream(new FileInputStream(file));
        fs.skip(offset);
        BitmapFactory.Options opts2 = new BitmapFactory.Options();
        opts2.inSampleSize = scale;
        bmp = BitmapFactory.decodeStream(fs, null, opts2);
    } finally {
        if (fs != null) {
            try {
                fs.close();
            } catch (IOException e) {
                // don't worry
            }
        }
    }
    return bmp;
}

From source file:Main.java

public static double logGamma(final double xx) {
    final double stp = 2.50662827465;
    final double[] cof = { 76.18009173, -86.50532033, 24.01409822, -1.231739516, 0.00120858003, -5.36382E-6 };
    double x = xx - 1.0;
    double tmp = x + 5.5;
    tmp = (x + 0.5) * Math.log(tmp) - tmp;
    double ser = 1.0;
    for (int j = 0; j < 6; ++j) {
        ++x;/*from  w  w  w . j  a  va2 s. c om*/
        ser += cof[j] / x;
    }
    final double retVal = tmp + Math.log(2.50662827465 * ser);
    return retVal;
}