public class StdStats {
/**
* Return maximum value in array, -infinity if no such value.
*/
public static double max(double[] a) {
double max = Double.NEGATIVE_INFINITY;
for (int i = 0; i < a.length; i++) {
if (a[i] > max) max = a[i];
}
return max;
}
/**
* Return maximum value in subarray a[lo..hi], -infinity if no such value.
*/
public static double max(double[] a, int lo, int hi) {
if (lo < 0 || hi >= a.length || lo > hi)
throw new RuntimeException("Subarray indices out of bounds");
double max = Double.NEGATIVE_INFINITY;
for (int i = lo; i <= hi; i++) {
if (a[i] > max) max = a[i];
}
return max;
}
/**
* Return maximum value of array, Integer.MIN_VALUE if no such value
*/
public static int max(int[] a) {
int max = Integer.MIN_VALUE;
for (int i = 0; i < a.length; i++) {
if (a[i] > max) max = a[i];
}
return max;
}
/**
* Return minimum value in array, +infinity if no such value.
*/
public static double min(double[] a) {
double min = Double.POSITIVE_INFINITY;
for (int i = 0; i < a.length; i++) {
if (a[i] < min) min = a[i];
}
return min;
}
/**
* Return minimum value in subarray a[lo..hi], +infinity if no such value.
*/
public static double min(double[] a, int lo, int hi) {
if (lo < 0 || hi >= a.length || lo > hi)
throw new RuntimeException("Subarray indices out of bounds");
double min = Double.POSITIVE_INFINITY;
for (int i = lo; i <= hi; i++) {
if (a[i] < min) min = a[i];
}
return min;
}
/**
* Return minimum value of array, Integer.MAX_VALUE if no such value
*/
public static int min(int[] a) {
int min = Integer.MAX_VALUE;
for (int i = 0; i < a.length; i++) {
if (a[i] < min) min = a[i];
}
return min;
}
/**
* Return average value in array, NaN if no such value.
*/
public static double mean(double[] a) {
if (a.length == 0) return Double.NaN;
double sum = sum(a);
return sum / a.length;
}
/**
* Return average value in subarray a[lo..hi], NaN if no such value.
*/
public static double mean(double[] a, int lo, int hi) {
int length = hi - lo + 1;
if (lo < 0 || hi >= a.length || lo > hi)
throw new RuntimeException("Subarray indices out of bounds");
if (length == 0) return Double.NaN;
double sum = sum(a, lo, hi);
return sum / length;
}
/**
* Return average value in array, NaN if no such value.
*/
public static double mean(int[] a) {
if (a.length == 0) return Double.NaN;
double sum = 0.0;
for (int i = 0; i < a.length; i++) {
sum = sum + a[i];
}
return sum / a.length;
}
/**
* Return sample variance of array, NaN if no such value.
*/
public static double var(double[] a) {
if (a.length == 0) return Double.NaN;
double avg = mean(a);
double sum = 0.0;
for (int i = 0; i < a.length; i++) {
sum += (a[i] - avg) * (a[i] - avg);
}
return sum / (a.length - 1);
}
/**
* Return sample variance of subarray a[lo..hi], NaN if no such value.
*/
public static double var(double[] a, int lo, int hi) {
int length = hi - lo + 1;
if (lo < 0 || hi >= a.length || lo > hi)
throw new RuntimeException("Subarray indices out of bounds");
if (length == 0) return Double.NaN;
double avg = mean(a, lo, hi);
double sum = 0.0;
for (int i = lo; i <= hi; i++) {
sum += (a[i] - avg) * (a[i] - avg);
}
return sum / (length - 1);
}
/**
* Return sample variance of array, NaN if no such value.
*/
public static double var(int[] a) {
if (a.length == 0) return Double.NaN;
double avg = mean(a);
double sum = 0.0;
for (int i = 0; i < a.length; i++) {
sum += (a[i] - avg) * (a[i] - avg);
}
return sum / (a.length - 1);
}
/**
* Return population variance of array, NaN if no such value.
*/
public static double varp(double[] a) {
if (a.length == 0) return Double.NaN;
double avg = mean(a);
double sum = 0.0;
for (int i = 0; i < a.length; i++) {
sum += (a[i] - avg) * (a[i] - avg);
}
return sum / a.length;
}
/**
* Return population variance of subarray a[lo..hi], NaN if no such value.
*/
public static double varp(double[] a, int lo, int hi) {
int length = hi - lo + 1;
if (lo < 0 || hi >= a.length || lo > hi)
throw new RuntimeException("Subarray indices out of bounds");
if (length == 0) return Double.NaN;
double avg = mean(a, lo, hi);
double sum = 0.0;
for (int i = lo; i <= hi; i++) {
sum += (a[i] - avg) * (a[i] - avg);
}
return sum / length;
}
/**
* Return sample standard deviation of array, NaN if no such value.
*/
public static double stddev(double[] a) {
return Math.sqrt(var(a));
}
/**
* Return sample standard deviation of subarray a[lo..hi], NaN if no such value.
*/
public static double stddev(double[] a, int lo, int hi) {
return Math.sqrt(var(a, lo, hi));
}
/**
* Return sample standard deviation of array, NaN if no such value.
*/
public static double stddev(int[] a) {
return Math.sqrt(var(a));
}
/**
* Return population standard deviation of array, NaN if no such value.
*/
public static double stddevp(double[] a) {
return Math.sqrt(varp(a));
}
/**
* Return population standard deviation of subarray a[lo..hi], NaN if no such value.
*/
public static double stddevp(double[] a, int lo, int hi) {
return Math.sqrt(varp(a, lo, hi));
}
/**
* Return sum of all values in array.
*/
public static double sum(double[] a) {
double sum = 0.0;
for (int i = 0; i < a.length; i++) {
sum += a[i];
}
return sum;
}
/**
* Return sum of all values in subarray a[lo..hi].
*/
public static double sum(double[] a, int lo, int hi) {
int length = hi - lo + 1;
if (lo < 0 || hi >= a.length || lo > hi)
throw new RuntimeException("Subarray indices out of bounds");
double sum = 0.0;
for (int i = lo; i <= hi; i++) {
sum += a[i];
}
return sum;
}
/**
* Return sum of all values in array.
*/
public static int sum(int[] a) {
int sum = 0;
for (int i = 0; i < a.length; i++) {
sum += a[i];
}
return sum;
}
/**
* Plot points (i, a[i]) to standard draw.
*/
public static void plotPoints(double[] a) {
int N = a.length;
StdDraw.setXscale(0, N-1);
StdDraw.setPenRadius(1.0 / (3.0 * N));
for (int i = 0; i < N; i++) {
StdDraw.point(i, a[i]);
}
}
/**
* Plot line segments connecting points (i, a[i]) to standard draw.
*/
public static void plotLines(double[] a) {
int N = a.length;
StdDraw.setXscale(0, N-1);
StdDraw.setPenRadius();
for (int i = 1; i < N; i++) {
StdDraw.line(i-1, a[i-1], i, a[i]);
}
}
/**
* Plot bars from (0, a[i]) to (i, a[i]) to standard draw.
*/
public static void plotBars(double[] a) {
int N = a.length;
StdDraw.setXscale(0, N-1);
StdDraw.setPenRadius(0.5 / N);
for (int i = 0; i < N; i++) {
// uses filled rectangle (instead of thick line, as in textbook)
StdDraw.filledRectangle(i, a[i]/2, .25, a[i]/2);
}
}
/**
* Test client.
* Convert command-line arguments to array of doubles and call various methods.
*/
public static void main(String[] args) {
double[] a = StdArrayIO.readDouble1D();
StdOut.printf(" min %7.3f\n", min(a));
StdOut.printf(" mean %7.3f\n", mean(a));
StdOut.printf(" max %7.3f\n", max(a));
StdOut.printf(" std dev %7.3f\n", stddev(a));
}
}
/*************************************************************************
* Execution: java StdStats < input.txt
*
* Library of statistical functions.
*
* The test client reads an array of real numbers from standard
* input, and computes the minimum, mean, maximum, and
* standard deviation.
*
* The functions all throw a NullPointerException if the array
* passed in is null.
* % more tiny.txt
* 5
* 3.0 1.0 2.0 5.0 4.0
*
* % java StdStats < tiny.txt
* min 1.000
* mean 3.000
* max 5.000
* std dev 1.581
*
*************************************************************************/
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