0

Hello everyone. I'm working on a project that acts as a function generator to output a sine wave. The program also outputs an excel file with all of the data points so one can plot the points. For some reason, when I add noise, the graph does not look right. Can anyone tell me why? I appreciate the help.

Here is my code:

```
#include "stdafx.h"
#include <stdio.h>
#include <tchar.h>
#include <iostream>
#include <math.h>
#include <conio.h>
#include <iomanip>
#include <time.h>
#include <stdlib.h>
#include <dos.h>
using namespace std;
void lab_7 (void)
{
srand((unsigned)time(0));
// declarations
FILE *fptr;
char fileName[50] = "";
double freq;
double gain;
double phase;
double bias;
double noise;
char save;
const long double PI = acos((long double) -1);
// user inputs for sine wave values
cout<<"Enter Frequency: [1-10Mhz] ";
cin>>freq;
cout<<"Enter Gain of Sine Wave: [1-10] ";
cin>>gain;
cout<<"Enter Phase Angle: [0-180] ";
cin>>phase;
cout<<"Enter Bias (offset) [+/- 10] ";
cin>>bias;
cout<<"Enter % Noise level introduced to sine (percent) [0 - 100%] ";
cin>>noise;
cout<<"Do you want to save the data [y/n]: ";
cin>>save;
if (save == 'y'){
cout<<"Enter a file name you wish to use: ";
cin>> fileName;
}
double timeint = (double)1/freq/360;
long double interval = (2*PI)/360;
long double sinevalue;
if (save = 'y') {
sprintf(fileName, "%s.csv", fileName);
fptr = fopen(fileName, "w");
fprintf(fptr, "%s,", "Time(1/f)");
fprintf(fptr, "%s\n", "Sine Pattern");
}
for(int i=0; i<=360; i++){
sinevalue = (gain*sin((interval*i)+phase)+(rand()*(noise/100)*gain))+bias;
if (save = 'y') {
fprintf(fptr, "%f,", timeint*i);
fprintf(fptr, "%f\n", sinevalue);
}
}
}
```