C++ code

[nathan.humphreys]

Hey, i'm trying to write a C++ code to calculate the standard deviation from an imput file that containts 3 columns of numbers, the x values, y values, and sigma (errors on each value), so far i have: /n/n

// include all headers needed here
#include <iostream>
#include <cmath>
#include <cctype>
#include <fstream>
#include <cstdlib>
#include <cstring>
using namespace std;


//declare sum here and link to calculation after main (prototype fucntion declaration)

int main (){

    //declare doubles here (what doubles do i need?)
    double x, y, sigma;

    // read the input and output filenames
    

    double a[1000][3];//x, y and sigma input values
    double b[1000][3];//x, y and sigma output values

    cout << "Please enter the input filename: " << endl;
    cin >> a;
    cout << "Please enter the output filename: " << endl;
    cin >> b;

    // declare array of structs, open input file and read sets of 3 numbers

    // (x, y sigma) into array

    ifstream in(a);
    // read the input and output filenames
    if(!in){
        cerr << "Failed to open input file " << a << endl;
        exit(1);
    }
        int j = sizeof(a)/sizeof(double)//no. of items in array

/n/nhow do i edit the data after i have stored it in the arrays?/b/bi am intending on putting an if function around the cin>>a to make sure that only numbers can be entered however i havnt got as far as that yet

[Rootstonian]

Is this a class assignment? If so, what specs did the teach give you? What's the name of the class?

Or, are you writing this on your own?

To me, it looks like a class assignment where the teach put in comments for you to "follow". Your code needs help

And if I remember correctly, file streams in C/C++ are all CHARACTER data! Reading 54.23, 76, 92.99, .02 and converting to doubles would be fun! It's been a while since I've had to code stuff like this (like that damn add/subtract polynomials of any x^n value; that was a BEATCH program!!!)

[nathan.humphreys]

i put those comments in so i know where i need to go, this is a class assignment but im pretty sure once i know how to edit the data stored in the arrays then i will be able to figure the rest out

[Rootstonian]

Ok, do me a favor; I call it "going back to basics".

Forget the files and the associated I/O.

Write the program to work with functions and hard-coded values:

double x1 = 2.2, x2 = 5.9, s1 = .01;
double y1 = 4.2, y2 = 15.99, s2 = 3.01;
double z1 = 22, z3 = 7.9, s3 = 9.01;

cout << "Standard Devivation = " compute_sd(x1, x2, s1) << endl;
cout << "Standard Devivation = " compute_sd(y1, y2, s2) << endl;
cout << "Standard Devivation = " compute_sd(z1, z2, s3) << endl;

There! 1/2 your program is done.
Now, right a SKELETON procedure that just opens a file and checks for success.
Then, put 3 intetgers into that that file; I forget syntax (that's why I have books), but the data is usually on one line space delimited (e.g. 3 15 6).
Code your file read loop (again, read your book...while !InFile.eof() { cin >> number[i]}:
Then replace code above (that worked with)
cout << "Standard Devivation = "compute_sd(number[i]) << endl;

I'll let you find out about C++ file I/O and character data vs. int vs. float data I've got my degrees LOL