Can someone explain why my program only prints out the same number?

Question

0.00/5 (No votes)

See more:

I only get the same number over and over again.

What I have tried:

C

// yprog.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#define ERROR 0
#define MAX_INPUT_LINE 80
#define SUCCESS 1

int main(int argc, char **argv)
{
	double mag = 0;
	double maxy = 0;
	double miny = 0;

	FILE *filein;
	char filein_name[MAX_INPUT_LINE];
	FILE *fileout;
	char fileout_name[MAX_INPUT_LINE];
	char input[MAX_INPUT_LINE];
	if (argc < 2)
	{
		printf("\n");
		printf("Yprog:\n");
		printf("  Enter the input file name :\n");

		if (fgets(input, MAX_INPUT_LINE, stdin) != NULL)
		{
			sscanf(input, "%s", filein_name);
		}
		else
		{
			printf("\n");
			printf("Yprog - Fatal error!\n");
			printf("  Input error!\n");
			return ERROR;
		}

		printf("\n");
		printf("Yprog:\n");
		printf("  Enter the output file name:\n");

		if (fgets(input, MAX_INPUT_LINE, stdin) != NULL)
		{
			sscanf(input, "%s", fileout_name);
		}
		else
		{
			printf("\n");
			printf("Yprog - Fatal error!\n");
			printf("  Input error!\n");
			return ERROR;
		}

		fileout = fopen(fileout_name, "w");

		if (fileout == NULL)
		{
			printf("\n");
			printf("Yprog - Fatal error!\n");
			printf("  Cannot open the output file %s.\n", fileout_name);
			return ERROR;
		}
	}
	else
	{
		strcpy(filein_name, argv[1]);
		fileout = stdout;
	}

	filein = fopen(filein_name, "r");

	if (filein == NULL)
	{
		printf("\n");
		printf("Yprog - Fatal error!\n");
		printf("  Cannot open the input file %s.\n", filein_name);
		return ERROR;
	}

	printf("Enter maximum value from file for y : ");
	scanf("%lg", &maxy);
	printf("Enter minimum value from file for y : ");
	scanf("%lg", &miny);

	// todo?

	{
		int n, c;
		double sum = 0, var;

		printf("Enter the number of sample values in the file minus 1.\n");	// 11025
		scanf("%d", &n);

		printf("using %d sample values.\n", n + 1);

		fseek(filein, 0, SEEK_SET);
		for (c = 0; c <= n; c = c + 1)
		{
			fscanf(filein, "%lg", &var);

			sum = var * (maxy / 65536.0);
			// todo?

			// todo?
			fprintf(fileout, "%lg\n", &sum);
		}
		getchar();
		fclose(filein);
		fclose(fileout);
		printf("Yprog: \n  File converted.\n");
		return 0;
	}

	return 0;
}

Posted 27-Aug-23 23:11pm

Richard C. Andrews

Updated 28-Aug-23 8:00am

Deeksha Shenoy

v3

Add a Solution

Comments

Richard MacCutchan 28-Aug-23 5:55am

What is contained in the input file, what are the values you enter, and what results do you see?

Richard C. Andrews 28-Aug-23 5:59am

It's just a long list of numbers gathered from an ADC with values ranging from +10 to -10.
The values printed (which is incorrect) have exponents too large to be reasonable.

Richard C. Andrews 28-Aug-23 6:01am

The goal is to squash the values in the file to a range of 1 to -1.

Richard MacCutchan 28-Aug-23 6:33am

Sorry but it's impossible to guess what the problem is. You need to use the debugger and check the results of each calculation.

Richard MacCutchan 28-Aug-23 6:56am

I have maxy = 10.0 and used the range -5 to +5. Using your calculations I get the following results:

val: -5, sum: -0.000762939
val: -4, sum: -0.000610352
val: -3, sum: -0.000457764
val: -2, sum: -0.000305176
val: -1, sum: -0.000152588
val: 0, sum: 0
val: 1, sum: 0.000152588
val: 2, sum: 0.000305176
val: 3, sum: 0.000457764
val: 4, sum: 0.000610352
val: 5, sum: 0.000762939

Which all look resonable.

CPallini 28-Aug-23 7:32am

You should report here the input values (an possibly the expected output) to get a meaningful help.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Andre Oosthuizen · Accepted Answer · 2023-08-28T04:19:00

Your issue is with your loop calculating and printing the same value because of how the value is printed using 'fprintf'. The format specifier '%lg' is used for reading a double value with 'fscanf', but when you print with 'fprintf', you should just use the variable 'sum' without the '&' operator -

C

fprintf(fileout, "%lg\n", sum);

You are also trying to scale the 'var' value using 'maxy' and '65536.0', but you're assigning the scaled value directly to 'sum' in each iteration of your loop. This means that in each iteration, 'sum' is being overwritten with a new value. To accumulate the scaled values, you should add the scaled value to 'sum' instead of assigning it -

C

sum += var * (maxy / 65536.0);

Your loop should look like this -

C

for (c = 0; c <= n; c = c + 1)
{
    fscanf(filein, "%lg", &var);

    sum += var * (maxy / 65536.0);

    fprintf(fileout, "%lg\n", sum);
}