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/*
* Stats.java
*
* Created on April 27, 2007, 10:42 AM
*
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
*/
package oms3.util;
import java.util.Arrays;
/**
*
* @author Olaf David
*/
public class Stats {
/** Creates a new instance of Stats */
private Stats() {
}
/** Normalized Vector.
*/
public static double norm_vec(double x, double y, double z) {
return Math.sqrt(x * x + y * y + z * z);
}
public static double max(double[] vals) {
double max = vals[0];
for (double v : vals) {
if (v > max) {
max = v;
}
}
return max;
}
public static double min(double[] vals) {
double min = vals[0];
for (double v : vals) {
if (v < min) {
min = v;
}
}
return min;
}
public static double range(double[] vals) {
double min = vals[0];
double max = vals[0];
for (double v : vals) {
if (v < min) {
min = v;
}
if (v > max) {
max = v;
}
}
return max - min;
}
public static int length(double[] vals) {
return vals.length;
}
public static double median(double[] vals) {
return quantile(vals, 0.5);
}
public static double mean(double[] vals) {
return sum(vals) / vals.length;
}
public static double stddev(double[] vals) {
double mean = mean(vals);
double squareSum = 0;
for (double v : vals) {
squareSum += v * v;
}
return Math.sqrt(squareSum / vals.length - mean * mean);
}
public static double stderr(double[] vals) {
return Math.sqrt(variance(vals) / vals.length);
}
public static double variance(double[] vals) {
double stddev = stddev(vals);
return stddev * stddev;
}
public static double meandev(double[] vals) {
double mean = mean(vals);
int size = vals.length;
double sum = 0;
for (int i = size; --i >= 0;) {
sum += Math.abs(vals[i] - mean);
}
return sum / size;
}
public static double sum(double[] vals) {
double sum = 0;
for (double v : vals) {
sum = sum + v;
}
return sum;
}
public static double product(double[] vals) {
double prod = 1;
for (double v : vals) {
prod = prod * v;
}
return prod;
}
public static double quantile(double[] vals, double phi) {
if (vals.length == 0) {
return 0.0;
}
double[] sortedElements = Arrays.copyOf(vals, vals.length);
Arrays.sort(sortedElements);
int n = sortedElements.length;
double index = phi * (n - 1);
int lhs = (int) index;
double delta = index - lhs;
double result;
if (lhs == n - 1) {
result = sortedElements[lhs];
} else {
result = (1 - delta) * sortedElements[lhs] + delta * sortedElements[lhs + 1];
}
return result;
}
/** Returns the lag-1 autocorrelation of a dataset;
*/
public static double lag1(double[] vals) {
double mean = mean(vals);
int size = vals.length;
double r1;
double q = 0;
double v = (vals[0] - mean) * (vals[0] - mean);
for (int i = 1; i < size; i++) {
double delta0 = (vals[i - 1] - mean);
double delta1 = (vals[i] - mean);
q += (delta0 * delta1 - q) / (i + 1);
v += (delta1 * delta1 - v) / (i + 1);
}
r1 = q / v;
return r1;
}
public static double rmse(double[] pred, double[] valid) {
double error = 0;
for (int i = 0; i < pred.length; i++) {
double diff = pred[i] - valid[i];
error += diff * diff;
}
error /= pred.length;
return Math.sqrt(error);
}
public static double bias(double[] pred, double[] valid) {
double sum = 0;
for (int i = 0; i < pred.length; i++) {
sum += pred[i] - valid[i];
}
return sum / sum(pred);
}
/** Calculates the efficiency between a test data set and a verification data set
* after Nash & Sutcliffe (1970). The efficiency is described as the proportion of
* the cumulated cubic deviation between both data sets and the cumulated cubic
* deviation between the verification data set and its mean value.
* @param prediction the simulation data set
* @param validation the validation (observed) data set
* @param pow the power for the deviation terms
* @return the calculated efficiency or -9999 if an error occurs
*/
public static double nashsut(double[] prediction, double[] validation, double pow) {
int pre_size = prediction.length;
int val_size = validation.length;
int steps = 0;
double sum_td = 0;
double sum_vd = 0;
/** checking if both data arrays have the same number of elements*/
if (pre_size != val_size) {
System.err.println("Prediction data and validation data are not consistent!");
return -9999;
} else {
steps = pre_size;
}
/**summing up both data sets */
for (int i = 0; i < steps; i++) {
sum_td = sum_td + prediction[i];
sum_vd = sum_vd + validation[i];
}
/** calculating mean values for both data sets */
double mean_td = sum_td / steps;
double mean_vd = sum_vd / steps;
/** calculating mean pow deviations */
double td_vd = 0;
double vd_mean = 0;
for (int i = 0; i < steps; i++) {
td_vd = td_vd + (Math.pow((Math.abs(validation[i] - prediction[i])), pow));
vd_mean = vd_mean + (Math.pow((Math.abs(validation[i] - mean_vd)), pow));
}
/** calculating efficiency after Nash & Sutcliffe (1970) */
double efficiency = 1 - (td_vd / vd_mean);
return efficiency;
}
/** Calculates the efficiency between the log values of a test data set and a verification data set
* after Nash & Sutcliffe (1970). The efficiency is described as the proportion of
* the cumulated cubic deviation between both data sets and the cumulated cubic
* deviation between the verification data set and its mean value.
* @param prediction the simulation data set
* @param validation the validation (observed) data set
* @param pow the power for the deviation terms
* @return the calculated log_efficiency or -9999 if an error occurs
*/
public static double nashsut_log(double[] prediction, double[] validation, double pow) {
int pre_size = prediction.length;
int val_size = validation.length;
int steps = 0;
double sum_log_pd = 0;
double sum_log_vd = 0;
/** checking if both data arrays have the same number of elements*/
if (pre_size != val_size) {
System.err.println("Prediction data and validation data are not consistent!");
return -9999;
} else {
steps = pre_size;
}
/** calculating logarithmic values of both data sets. Sets 0 if data is 0 */
double[] log_preData = new double[pre_size];
double[] log_valData = new double[val_size];
for (int i = 0; i < steps; i++) {
if (prediction[i] < 0) {
System.err.println("Logarithmic efficiency can only be calculated for positive values!");
return -9999;
}
if (validation[i] < 0) {
System.err.println("Logarithmic efficiency can only be calculated for positive values!");
return -9999;
}
if (prediction[i] == 0) {
log_preData[i] = 0;
} else {
log_preData[i] = Math.log(prediction[i]);
}
if (validation[i] == 0) {
log_valData[i] = 0;
} else {
log_valData[i] = Math.log(validation[i]);
}
}
/**summing up both data sets */
for (int i = 0; i < steps; i++) {
sum_log_pd = sum_log_pd + log_preData[i];
sum_log_vd = sum_log_vd + log_valData[i];
}
/** calculating mean values for both data sets */
double mean_log_pd = sum_log_pd / steps;
double mean_log_vd = sum_log_vd / steps;
/** calculating mean pow deviations */
double pd_log_vd = 0;
double vd_log_mean = 0;
for (int i = 0; i < steps; i++) {
pd_log_vd = pd_log_vd + (Math.pow(Math.abs(log_valData[i] - log_preData[i]), pow));
vd_log_mean = vd_log_mean + (Math.pow(Math.abs(log_valData[i] - mean_log_vd), pow));
}
/** calculating efficiency after Nash & Sutcliffe (1970) */
double log_efficiency = 1 - (pd_log_vd / vd_log_mean);
return log_efficiency;
}
public static double err_sum(double[] validation, double[] prediction) {
double volError = 0;
for (int i = 0; i < prediction.length; i++) {
volError += (prediction[i] - validation[i]);
}
return volError;
}
/** Calculates the index of agreement (ioa) between a test data set and a verification data set
* after Willmot & Wicks (1980). The ioa is described as the proportion of
* the cumulated cubic deviation between both data sets and the squared sum of the absolute
* deviations between the verification data set and the test mean value and the test data set and
* its mean value.
* @param prediction the test Data set
* @param validation the verification data set
* @param pow the power
* @return the calculated ioa or -9999 if an error occurs
*/
public static double ioa(double[] prediction, double[] validation, double pow) {
double ioa;
int td_size = prediction.length;
int vd_size = validation.length;
if (td_size != vd_size) {
throw new IllegalArgumentException("Data sets in ioa does not match!");
}
int steps = td_size;
double sum_td = 0;
double sum_vd = 0;
/**summing up both data sets */
for (int i = 0; i < steps; i++) {
sum_td = sum_td + prediction[i];
sum_vd = sum_vd + validation[i];
}
/** calculating mean values for both data sets */
double mean_td = sum_td / steps;
double mean_vd = sum_vd / steps;
/** calculating mean cubic deviations */
double td_vd = 0;
double vd_mean = 0;
for (int i = 0; i < steps; i++) {
td_vd = td_vd + (Math.pow((Math.abs(validation[i] - prediction[i])), pow));
vd_mean = vd_mean + (Math.pow((Math.abs(validation[i] - mean_vd)), pow));
}
/** calculating absolute squared sum of deviations from verification mean */
double ad_test = 0;
double ad_veri = 0;
double abs_sqDevi = 0;
for (int i = 0; i < steps; i++) {
abs_sqDevi = abs_sqDevi + Math.pow(Math.abs(prediction[i] - mean_vd) + Math.abs(validation[i] - mean_vd), pow);
}
/** calculating ioa */
ioa = 1.0 - (td_vd / abs_sqDevi);
return ioa;
}
/**
* Calcs coefficients of linear regression between x, y data
* @param xData the independent data array (x)
* @param yData the dependent data array (y)
* @return (intercept, gradient, r2)
*/
private static double[] calcLinReg(double[] xData, double[] yData) {
double sumX = 0;
double sumY = 0;
double prod = 0;
int nstat = xData.length;
double[] regCoef = new double[3]; //(intercept, gradient, r2)
double meanYValue = mean(yData);
double meanXValue = mean(xData);
//calculating regression coefficients
for (int i = 0; i < nstat; i++) {
sumX += (xData[i] - meanXValue) * (xData[i] - meanXValue);
sumY += (yData[i] - meanYValue) * (yData[i] - meanYValue);
prod += (xData[i] - meanXValue) * (yData[i] - meanYValue);
}
if (sumX > 0 && sumY > 0) {
regCoef[1] = prod / sumX; //gradient
regCoef[0] = meanYValue - regCoef[1] * meanXValue; //intercept
regCoef[2] = Math.pow((prod / Math.sqrt(sumX * sumY)), 2); //r2
}
return regCoef;
}
public static double intercept(double[] xData, double[] yData) {
return calcLinReg(xData, yData)[0];
}
public static double gradient(double[] xData, double[] yData) {
return calcLinReg(xData, yData)[1];
}
public static double r2(double[] xData, double[] yData) {
return calcLinReg(xData, yData)[2];
}
/**
* Round a double value to a specified number of decimal
* places.
*
* @param val the value to be rounded.
* @param places the number of decimal places to round to.
* @return val rounded to places decimal places.
*/
public static double round(double val, int places) {
long factor = (long) Math.pow(10, places);
// Shift the decimal the correct number of places
// to the right.
val = val * factor;
// Round to the nearest integer.
long tmp = Math.round(val);
// Shift the decimal the correct number of places
// back to the left.
return (double) tmp / factor;
}
/**
* Round a float value to a specified number of decimal
* places.
*
* @param val the value to be rounded.
* @param places the number of decimal places to round to.
* @return val rounded to places decimal places.
*/
public static float round(float val, int places) {
return (float) round((double) val, places);
}
/**
* Generate a random number in a range.
*
* @param min
* @param max
* @return the random value in the min/max range
*/
public static double random(double min, double max) {
assert max > min;
return min + Math.random() * (max - min);
}
}
