Page Menu
Home
c4science
Search
Configure Global Search
Log In
Files
F78976132
ch-05-ex-04-solution.cpp
No One
Temporary
Actions
Download File
Edit File
Delete File
View Transforms
Subscribe
Mute Notifications
Award Token
Subscribers
None
File Metadata
Details
File Info
Storage
Attached
Created
Sat, Aug 24, 02:13
Size
2 KB
Mime Type
text/x-c
Expires
Mon, Aug 26, 02:13 (1 d, 21 h)
Engine
blob
Format
Raw Data
Handle
20130566
Attached To
R9360 PCSC_git
ch-05-ex-04-solution.cpp
View Options
/*
* chapter-05-exercise-04.cpp
*
* Standard deviation of array
* Input the array as extra command line arguments:
* ./ch-05-ex-04-solution 5.0 4.8 5.3 2.9
*
* Created on: Oct 8, 2012
* Author: Radu Popescu <radu.popescu@epfl.ch>
*/
#include <cmath>
#include <cstdlib>
#include <iostream>
void mean_and_std(const double *const v, const double size, double &mean,
double &stdev) {
mean = 0.0;
for (int i = 0; i < size; ++i) {
mean += v[i];
}
mean /= size;
double s1 = 0.0;
for (int i = 0; i < size; ++i) {
s1 += std::pow(v[i] - mean, 2);
}
stdev = std::sqrt(s1 / (size - 1));
}
/*
* This function computes the mean and standard deviation of a series
* of floating point numbers using a recurrence relation.
* This is useful for continuous processes and is resistant to round-off
* error.
*
* Attributed to B.P. Welford, Technometrics, 4,(1962), 419-420.
*/
void mean_and_std_rec(const double *const v, const double size, double &mean,
double &stdev) {
double mean_prev = v[0];
double stdev_accum = 0.0;
double mean_next = 0.0;
for (int i = 1; i < size; ++i) {
mean_next = mean_prev + (v[i] - mean_prev) / (i + 1);
stdev_accum += (v[i] - mean_prev) * (v[i] - mean_next);
mean_prev = mean_next;
}
mean = mean_next;
stdev = std::sqrt(stdev_accum / (size - 1));
}
int main(int argc, char *argv[]) {
if (argc == 1) {
std::cout << "Please input a series of floating point numbers:\n"
<< " ./ch-05-ex-04-solution 5.0 4.8 5.3 2.9" << std::endl;
return -1;
}
const int n = argc - 1;
double *const v = new double[n];
for (int i = 0; i < n; ++i) {
v[i] = std::atof(argv[i + 1]);
}
double mean;
double std_deviation;
mean_and_std(v, n, mean, std_deviation);
std::cout << "The mean and standard deviation are: " << mean << " and "
<< std_deviation << std::endl;
mean_and_std_rec(v, n, mean, std_deviation);
std::cout << "The mean and standard deviation are: " << mean << " and "
<< std_deviation << std::endl;
delete[] v;
return 0;
}
Event Timeline
Log In to Comment