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closed account (4wpL6Up4)
Hi,
I need the code for the roughness formula, I can't find it anywhere.
The list of numbers I have to use are in a txt file.

lastchance (6980)
the roughness formula


???

The list of numbers I have to use are in a txt file.


??????

Not one of your more intelligible posts @nypran.
closed account (4wpL6Up4)
ok, I will try to rephrase:

how to extract numbers from a txt file, obtain their individual absolute value and then sum these values?
lastchance (6980)
nypran wrote:
how to extract numbers from a txt file, obtain their individual absolute value and then sum these values?


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#include <iostream>
#include <sstream>
#include <fstream>
#include <cstdlib>
using namespace std;

int main()
{
// ifstream in( "input.txt" );              // Actual input file
   stringstream in( "1 -2 3 -4 5 -6" );     // Fake input file
   int sum = 0;
   for ( int n; in >> n; ) sum += abs( n );
   cout << sum;
}


But I'd love to know what on earth that had to do with roughness.
Last edited on
closed account (4wpL6Up4)
Here is what I have tried so far.
However, something doesn't seem right.
The minimum value that I obtained is not as small as the smallest
present in the txt file.
The txt file contains 126 numbers but my code counted 121.
and the formulas I wrote I suspect they are incorrect.

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#include "pch.h"
#include <iostream>
#include <fstream>
#include <string>
#include<cmath>

using namespace std;
int main()
{

	ifstream myfile("surfacedata.txt");

	if (myfile.good())
	{
		double n;
		int sum = 0;
		double count = -5.0;
		double max = 0;
		double min = -5.0;
		while (myfile >> n)
		{

			sum += n;
			count++;
			if (n > max)
				max = n;

			min = n;
			if (n < min)
				min = n;
		}



		
		cout << " the number values is " << " " << count << "." << "the largest value is " << "." << max << "." << endl;
			cout<<"the smallest value is"<<min << "the sum is" << "." << sum << endl;

			double ra = (abs(n)) / count; //sum of abs value of each number in the file, divided by how many numbers

			double rq = sqrt(pow(n, 2) / count); //square root of (sum of the square of each number in the file divided by how many numbers)

			double mr = abs(min) + max;

			cout << "r1=" << ra << "r2=" << rq << "r3=" << mr << endl;

	}
	else
	{
		cout << "\nFailed to open the file surfacedata.txt!";
	}
	myfile.close();
	system("PAUSE");
	return 0;
}
lastchance (6980)
@nypran, that code bears absolutely no resemblance to what you asked in your first two posts of the thread.

Anyway, ...

Lines 18 and 19 presuppose rather a lot about the range of values in the file. I would initialise them with the first point read.

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		min = n;
			if (n < min)
Nope, I can't see that working.

You read a succession of numbers in (line 20). At the end of that reading, the value of n is whatever number you read last from file. So what you do on lines 39ff is done entirely on the basis of the last number read from file. Which, I suspect, is not what you want. But since I still haven't a clue what you do want I can't really say any more.

PLEASE PHRASE YOUR QUESTIONS SO THAT THEY ARE INTELLIGIBLE. Maybe a more specific title to the thread might be in order, too; it looks more like an SOS.
Last edited on
closed account (4wpL6Up4)
the n used in the formula is basically the value of the numbers that are contained in the txt file, and count is how many numbers.
Enoizat (1343)
nypran, just keep your code a bit tidier and you can easily spot the biggest problem by yourself:

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#include <cmath>
#include <iostream>
#include <fstream>
#include <string>


int main()
{
    const std::string fname { "nypran.dat" };
    std::ifstream myfile(fname);
    if(!fname) {
        std::cout << "Failed to open the file " << fname << "!\n";
        return 0;
    }

    double n;
    int sum = 0;
    double count = -5.0;
    double max = 0;
    double min = -5.0;

    while (myfile >> n) // ------------------------------------------------------ //
    {                                                                             //
        sum += n;                                                                 //
        count++;                                                                  //
        if (n > max) {                                                            //
            max = n;                                                              //
        }                                                                         //
        min = n;                                                                  //
        if (n < min) {                                                            //
            min = n;                                                              //
        }                                                                         //
                                                                                  //
        std::cout << "The number values is "     << count                         //
                  << ".\nThe largest value is "  << max                           //
                  << ".\nThe smallest value is " << min                           //
                  << ".\nThe sum is "            << sum << ".\n";                 //
                                                                                  //
        // sum of abs value of each number in the file, divided by how many       //
        // numbers:                                                               //
        double ra = (abs(n)) / count;                                             //
                                                                                  //
        // square root of (sum of the square of each number in the file divided   //
        // by how many numbers)                                                   //
        double rq = sqrt(pow(n, 2) / count);                                      //
                                                                                  //
        double mr = abs(min) + max;                                               //
                                                                                  //
        std::cout << "r1 = " << ra << "; r2 = " << rq << "; r3 = " << mr << '\n'; //
    }   // ---------------------------------------------------------------------- //
    myfile.close();
    return 0;
}


I think the main problem is you should wait your reading-from-file loop has ended before performing any calculation (or even output) on your data.

I’d also cut down on ‘tautological’ comments - I mean, when the code is pretty clear itself, comments are usually unnecessary.

May I ask you what are you trying to calculate (just to prove my ignorance at math)?
Because:
1) “sum of abs value of each number in the file, divided by how many numbers”
--> is pretty similar to the arithmetic mean, apart from the ‘abs’.

2) “square root of (sum of the square of each number in the file divided by how many numbers)”
--> this somehow resemble the geometric mean, but in that case, I think it is wrong.
dhayden (5798)
The txt file contains 126 numbers but my code counted 121.
The file might have extraneous characters in it. Add this after the while loop:
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if (!myfile.eof()) {
    cout << "Syntax error after reading " << count << " items\n";
    return 1;
}

//sum of abs value of each number in the file, divided by how many
//square root of (sum of the square of each number in the file divided by how many numbers)

For these you'll need to keep a running sum of the absolute values and the squares:
Lines 16 & 17: Why is n a double and sum an int? They should be the same type.
Line 18: Why do you initialize count to -5? Why is it a double?

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#include <cmath>
#include <iostream>
#include <fstream>
#include <string>

int
main()
{
    double n;
    double sumAbs = 0;		// sum of abs(n)
    double sumSq = 0;		// sum of n^2
    unsigned count = 0;		// number of numbers read
    double max = 0;
    double min = -5.0;
    bool first = true;
    while (std::cin >> n) {		 // Note that I'm reading from cin. It's much more flexible
	count++;
	sumAbs += abs(n);
	sumSq += n * n;
	if (first) {
	    first = false;
	    min = max = n;
	} else {
	    if (n > max) {
		max = n;
	    }
	    if (n < min) {
		min = n;
	    }
	}
    }
    if (!std::cin.eof()) {
	std::cout << "syntax error after reading " << count << "items\n";
	return 1;
    }

    std::cout << "The number values is " << count
	      << ".\nThe largest value is " << max
	      << ".\nThe smallest value is " << min
	      << ".\nThe sum of absolute values is " << sumAbs << ".\n";

    // sum of abs value of each number in the file, divided by how many
    // numbers:
    double ra = sumAbs / count;

    // square root of (sum of the square of each number in the file divided   //
    // by how many numbers)                                                   //
    double rq = sqrt(sumSq) / count;
    double mr = abs(min) + max;

    std::cout << "r1 = " << ra << "; r2 = " << rq << "; r3 = " << mr << '\n';	//

    return 0;
}


$ ./foo < input.txt
The number values is 5.
The largest value is 12345.
The smallest value is -45.333.
The sum of absolute values is 12461.
r1 = 2492.2; r2 = 2469.04; r3 = 12390

lastchance (6980)
@nypran, it looks from your notation as if you are after these parameters:
https://en.wikipedia.org/wiki/Surface_roughness#Amplitude_parameters

Note that they are phrased in terms of deviation from the mean. I don't see you subtracting the mean anywhere.
lastchance (6980)
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#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>
#include <valarray>
#include <cassert>
using namespace std;

int main()
{
   string filename = "surfacedata.txt";
   vector<double> rawY;

   // Read data
// ifstream in( filename );   assert( in );           // File
   stringstream in( "1  2  3  4  5  6" );             // For demonstration
   for ( double x; in >> x; ) rawY.push_back( x );
   int N = rawY.size();

   // Switch to valarray for convenience
   valarray<double> y( N );
   for ( int i = 0; i < N; i++ ) y[i] = rawY[i];

   // Subtract the mean: we are looking at deviations
   y -= y.sum() / N;

   cout << "Measures of spread:\n";
   cout << "Ra = " << abs( y ).sum() / N << '\n';                // Mean absolute deviation
   cout << "Rq = " << sqrt( ( y * y ).sum() / N ) << '\n';       // RMS deviation
   cout << "Rv = " << y.min() << '\n';                           // Valley depth (NOTE: not convinced)
   cout << "Rp = " << y.max() << '\n';                           // Peak height 
   cout << "Rt = " << y.max() - y.min() << '\n';                 // Range
}


surfacedata.txt 
1  2  3  4  5  6


Measures of spread:
Ra = 1.5
Rq = 1.70783
Rv = -2.5
Rp = 2.5
Rt = 5


Last edited on
Enoizat (1343)
lastchance wrote:
@nypran, it looks from your notation as if you are after these parameters:
https://en.wikipedia.org/wiki/Surface_roughness#Amplitude_parameters

Mystery solved… :-)

+1 lastchance (as usual!)
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