Thread: Printing random decimal numbers in a text file

Hi,

I am trying to create a simple program that can generate numbers in a separate .txt file.

The random numbers generated should be:
1. normalised (if i am not mistaken, it should be divided by 32767) to be within the range of -1.000000 to 1.000000
2. up to 6 decimal places

However I encountered a couple of problems:
1. The random numbers I generate are whole numbers (when what I want are random numbers up to 6 decimal places)
2. When I try to normalise the numbers (i.e. divide it by 32767), all my numbers become 0.00000

Here is the program:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include <time.h>

double main() 
{
  double i;
  FILE *file;     

  file = fopen("numbers.txt", "w"); 

  if(file==NULL) {
    printf("An error has occurred.\n");
    return 1;
  }
  
	srand(time(NULL));

  for(i=0 ; i<1000 ; i++) /* 1000 random numbers to be generated*/
  {

	double random;

  random = (rand()%32767+1)/32767; 
 
    fprintf(file, "%lf\n", random); 
    
  }

  fclose(file); 
  return 0;
}

Hope someone would be able to help!

Thanks!

Yeah. you made mistake in calculation.
random = (rand()%32767+1)/32767;

It takes 32767 values integer and this (rand()%32767+1) value as float. so it returns 0.000000

Change the calculation like this it will work.

Code:

random = (rand()%32767+1)/32767.0f;

Now, it will take both values are float. so it will generate random numbers.

Thanks it works!

I have another problem:
I would like to now print these numbers in an array (with a 'tab' spacing in between the numbers). Any suggestions in editing the code?

I should look something like (in the text file):
0.123456 0.234567 0.345678
0.789456 0.456232 0.756159
... ...