Program to Print Histogram in C

The program accepts an array as input and prints a histogram. It uses srand() method for random data creation ranging from 0 to 20 elements.

We need to generate a frequency array for 100 numbers between 0-19. Further, we need to create, add data and print a corresponding histogram for same.

Program to Print Histogram in C

Program:

/******************************************************************************

    Program to print histogram from given array in C                

*******************************************************************************/
#include<stdio.h>
#include <stdlib.h>
#include<time.h>
int main ()
{

  int arr[100], i, barSize, p, count;

  // Variables that are being used for printing histogram 

  int firstBar = 0, secBar = 0, thirdBar = 0, fourthBar = 0, lowerRange =
    0, upperRange = 5;

  // srand for creating random values between 0 to 20 

  srand (time (0));
  for (i = 0; i < 100; i++){
      arr[i] = rand () % 20;
    }


// printing autogenerated array elements on output screen    
      printf ("Array values for the histogram :: \n");

  for (i = 0; i < 100; i++){
      printf ("%d  ", arr[i]);
    }


// printing histogram in C  by spliting bar in intervals of 5 i.e 0-5, 5-10
  for (i = 0; i < 100; i++){
      if (arr[i] < 5){
    firstBar = firstBar + 1;
  }
      else if ((arr[i] < 10) && (arr[i] > 5)){
    secBar = secBar + 1;
  }
      else if ((arr[i] < 15) && (arr[i] > 10)){
    thirdBar = thirdBar + 1;
  }
      else{
    fourthBar = fourthBar + 1;
  }
    }
    
    // Printing histogram in C
    
  printf ("\n\n*************** HISTOGRAM ***************\n\n");
  i = 1;
  barSize = firstBar;
  
  while (i <= 4){
      printf ("\n     |\n%2d-%2d|", lowerRange, upperRange);
      p = 1;
      while (p <= barSize){
    printf ("*");
    p++;
  }
  
      printf ("\n     |\n");
      if (i == 2)
  barSize = secBar;
      if (i == 3)
       barSize = thirdBar;
      if (i == 4)
       barSize = fourthBar;
         lowerRange = lowerRange + 5;
         upperRange = upperRange + 5;
         i++;
    }
  return 0;
}

Output:

Random data inputs are generated first:-

Array values for the histogram :: 
6  18  0  9  16  16  17  6  3  10  6  18  13  6  5  15  7  5  17  9  15  6  16  7  15  14  0  0  12  8  12  18  18  12  7  14  0  17  0  15  7  19  13  12  5  10  0  4  15  17  14  2  15  10  9  10  17  2  2  1  2  14  0  0  18  19  14  19  16  6  14  15  5  8  0  2  10  0  19  6  17  13  0  13  15  2  15  4  4  18  6  6  4  18  6  3  9  12  14  18

Plotted to Histogram:

*************** HISTOGRAM ***************


     |
 0- 5|************************
     |

     |
 5-10|************************
     |

     |
10-15|********************
     |

     |
15-20|****************
     |

Explanation:

1. We have generated frequency data, with values ranging from 0 to 19
2. To create a histogram, we have used intervals 0-5,5- 10, 10-15, 15-20 with 5 class size
3. In order to create 4 bars, we have used 4 variables named, firstBar, secBar, thirdBar, and fourthBar
4. While iterating frequency data, if the value lies between 0 to 5, count it as 1 and add it to the first bar
5. Similarly, if it ranges from 5 to 10, then add 1 to secBar variable
6. Lastly, we have printed the histogram on the output screen