C Tutor... C Tutorial....: Generating a bar chart in C

 

#include 

#include 

#include 

#include 



#define PAGE_HEIGHT  20

#define PAGE_WIDTH   40



typedef struct barTAG

{

  double value;

  struct barTAG *pnextbar;

}bar;



typedef unsigned int uint;     /* Type definition*/



/* Function prototype */

int bar_chart(bar *pfirstbar, uint page_width, uint page_height, char *title);



int main(void)

{

  bar firstbar;            /* First bar structure */

  bar *plastbar = NULL;    /* Pointer to last bar */

  char value[80];          /* Input buffer        */

  char title[80];          /* Chart title         */



  printf("\nEnter the chart title: ");

  gets(title);             /* Read chart title    */



  for( ;; )                /* Loop for bar input  */

  {

    printf("Enter the value of the bar, or use quit to end: ");

    gets(value);



    if(strcmp(value, "quit") == 0)   /* quit entered?       */

     break;                          /* then input finished */



    /* Store in next bar */

    if(!plastbar)                /* First time?             */

    {

      firstbar.pnextbar = NULL;  /* Initialize next pointer */

      plastbar = &firstbar;      /* Use the first           */

    }

    else

    {

      /* Get memory */

      if(!(plastbar->pnextbar = malloc(sizeof(bar))))

      {

        printf("Oops! Couldn't allocate memory\n");

        return -1;

      }

      plastbar = plastbar->pnextbar;    /* Old next is new bar  */

      plastbar->pnextbar = NULL;        /* New bar next is NULL */

    }

    plastbar->value = atof(value);      /* Store the value      */

  }



  /* Create bar-chart */

  bar_chart(&firstbar, PAGE_WIDTH, PAGE_HEIGHT, title);



  /* We are done, so release all the memory we allocated */

  while(firstbar.pnextbar)

  {

    plastbar = firstbar.pnextbar;           /* Save pointer to next */

    firstbar.pnextbar = plastbar->pnextbar; /* Get one after next   */

    free(plastbar);                         /* Free next memory     */

  }

  return 0;

}



int bar_chart(bar *pfirstbar, uint page_width, uint page_height,

                                                       char *title)

{

  bar *plastbar = pfirstbar;  /* Pointer to previous bar         */

  double max = 0.0;           /* Maximum bar value               */

  double min = 0.0;           /* Minimum bar value               */

  double vert_scale = 0.0;    /* Unit step in vertical direction */

  double position = 0.0;      /* Current vertical position on chart */

  uint bar_count = 1;         /* Number of bars - at least 1     */

  uint barwidth = 0;          /* Width of a bar                  */

  uint space = 2;             /* spaces between bars             */

  uint i = 0;                 /* Loop counter                    */

  uint bars = 0;              /* Loop counter through bars       */

  char *column = NULL;        /* Pointer to bar column section   */

  char *blank = NULL;         /* Blank string for bar+space      */

  bool axis = false;          /* Indicates axis drawn            */

  /* Find maximum and minimum of all bar values */



  /* Set max and min to first bar value */

  max = min = plastbar->value;



  while((plastbar = plastbar->pnextbar) != NULL)

  {

    bar_count++;              /* Increment bar count */

    max = (max < plastbar->value)? plastbar->value : max;

    min = (min > plastbar->value)? plastbar->value : min;

  }

  vert_scale = (max - min)/page_height; /* Calculate step length */



  /* Check bar width */

  if((barwidth = page_width/bar_count - space) < 1)

  {

    printf("\nPage width too narrow.\n");

    return -1;

  }



  /* Set up a string that will be used to build the columns */



  /* Get the memory */

  if((column = malloc(barwidth + space + 1)) == NULL)

  {

    printf("\nFailed to allocate memory in barchart()"

                           " - terminating program.\n");

    exit(1);

  }

  for(i = 0 ; i    *(column+i)=' ';         /* Blank the space between bars */

  for( ; i    *(column+i)='#';         /* Enter the bar characters     */

  *(column+i) = '\0';        /* Add string terminator        */



  /* Set up a string that will be used as a blank column */



  /* Get the memory */

  if((blank = malloc(barwidth + space + 1)) == NULL)

  {

    printf("\nFailed to allocate memory in barchart()"

                           " - terminating program.\n");

    exit(1);

  }



  for(i = 0 ; i    *(blank+i) = ' ';        /* Blank total width of bar+space */

  *(blank+i) = '\0';         /* Add string terminator          */



    printf("^ %s\n", title);   /* Output the chart title      */



  /* Draw the bar chart */

  position = max;

  for(i = 0 ; i <= page_height ; i++)

  {

    /* Check if we need to output the horizontal axis */

    if(position <= 0.0 && !axis)

    {

      printf("+");           /* Start of horizontal axis    */

      for(bars = 0; bars < bar_count*(barwidth+space); bars++)

        printf("-");         /* Output horizontal axis      */

      printf(">\n");

      axis = true;           /* Axis was drawn              */

      position -= vert_scale;/* Decrement position           */

      continue;

    }

    printf("|");             /* Output vertical axis        */

    plastbar = pfirstbar;    /* start with the first bar    */



    /* For each bar... */

    for(bars = 1; bars <= bar_count; bars++)

    {

      /* If position is between axis and value, output column */

      /* otherwise output blank                               */

      printf("%s", position <= plastbar->value &&

                    plastbar->value >= 0.0 && position > 0.0 ||

                    position >= plastbar->value &&

                    plastbar->value <= 0.0 &&

                    position <= 0.0 ? column: blank);

      plastbar = plastbar->pnextbar;

    }

    printf("\n");            /* End the line of output        */

    position -= vert_scale;  /* Decrement position            */

  }

  if(!axis)            /* Have we output the horizontal axis? */

  {                    /* No, so do it now                    */

    printf("+");

    for(bars = 0; bars < bar_count*(barwidth+space); bars++)

      printf("-");

    printf(">\n");

  }



  /* Code for rest of the function...  */

  free(blank);               /* Free memory for blank string   */

  free(column);              /* Free memory for column string  */

  return 0;

}