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Program3

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Dec 7th, 2010
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  1. /*
  2.  
  3.  *  prog3A.c
  4.  
  5.  * 
  6.  
  7.  *  Calculates the integral of cos^2(x).
  8.  
  9.  *
  10.  
  11.  *  Input command line argument of upper limit between 0 and Pi/2.
  12.  
  13.  *  Lower limit is set by default to 0.
  14.  
  15.  */
  16.  
  17.  
  18.  
  19. #include <stdio.h>
  20.  
  21. #include <stdlib.h>
  22.  
  23. #include <math.h>
  24.  
  25. #define NODATA "There was not one argument entered. Exiting...\n"
  26.  
  27. #define INVALID "The data entered was not valid. Entered value must be between 0 and Pi/2\n"
  28.  
  29. #define LOWERLIMIT 0
  30.  
  31. #define MAXLIMIT M_PI/2
  32.  
  33. #define FILENAME "px270prog3a.dat"
  34.  
  35. #define RESULT "The integral of (Cos(x))^2 between %lf and %lf is %lf\n"
  36.  
  37. #define DEBUG 0
  38.  
  39.  
  40.  
  41. void integrate(double *xvalues, double *fvalues, int count, double low , double high, double *integral);
  42.  
  43.  
  44.  
  45. int main(int argc, char* argv[]) {
  46.  
  47.     /*Values*/
  48.  
  49.     double a,b,value,dummy;
  50.  
  51.     double *xvalues, *fvalues,integral;
  52.  
  53.     /*Counts*/
  54.  
  55.     int size=0,count=0,entrycount=0;
  56.  
  57.     /*Flags*/
  58.  
  59.     int rightnumber=0,validInput;
  60.  
  61.     /*File*/
  62.  
  63.     FILE* input;
  64.  
  65.    
  66.  
  67.     /*Set Lower Limit*/
  68.  
  69.     a = LOWERLIMIT;
  70.  
  71.     /*Check and then read command line arguments */
  72.  
  73.     if ((argc < 2)||(argc > 2)){
  74.  
  75.         printf(NODATA);
  76.  
  77.         exit(EXIT_FAILURE);
  78.  
  79.     }
  80.  
  81.     else {
  82.  
  83.         sscanf(argv[1],"%lf", &b);
  84.  
  85.     }
  86.  
  87.     /*Test for valid input. If not valid, exit*/
  88.  
  89.     validInput = ((b > LOWERLIMIT) && (b < MAXLIMIT) && (b != EOF));
  90.  
  91.     if(!validInput){
  92.  
  93.         printf(INVALID);
  94.  
  95.         exit(EXIT_FAILURE);
  96.  
  97.     }
  98.  
  99.     /*Open file, read data from file*/
  100.  
  101.     input = fopen(FILENAME,"r");
  102.  
  103.     /*Scan through the file once, to help work out size of array needed*/
  104.  
  105.     while (rightnumber == 0){
  106.  
  107.         fscanf(input," %lf ",&value);
  108.  
  109.         fscanf(input," %lf ",&dummy);
  110.  
  111.         count++;
  112.         printf("Count = %d \n",count);
  113.  
  114.         /*If the value read for x is greater than the upper limit, stop counting data*/
  115.  
  116.         if (value >= b) {
  117.  
  118.             rightnumber = 1;
  119.  
  120.             rewind(input);
  121.  
  122.         }
  123.  
  124.     }
  125.  
  126.     /*Set the size of the arrays*/
  127.  
  128.     size = (count+1)*(sizeof(double));
  129.  
  130.     xvalues = (double*)malloc(size);
  131.  
  132.     fvalues = (double*)malloc(size);
  133.  
  134.     /*Use fscanf to fill arrays with values*/
  135.  
  136.     while (entrycount<=count) {
  137.  
  138.         fscanf(input,"%lf",&xvalues[entrycount]);
  139.  
  140.         fscanf(input,"%lf",&fvalues[entrycount]);
  141.  
  142.         entrycount++;
  143.         //printf("Entrycount = %lf, Xvalues = %lf, FXVALues = %lf \n",entrycount,xvalues[entrycount],fvalues[entrycount]);
  144.  
  145.     }
  146.  
  147.     fclose(input);
  148.  
  149.     /*Call integrate function, using pointer for integral, print result*/
  150.  
  151.     integrate(xvalues,fvalues,count+1,a,b,&integral);
  152.  
  153.     printf(RESULT,a,b,integral);
  154.  
  155.    
  156.  
  157.     return 0;
  158.  
  159. }
  160.  
  161.        
  162.  
  163. void integrate(double *xvalues, double *fvalues, int length, double lowlim , double uplim, double *integral){
  164.  
  165.     double workinginteg;
  166.  
  167.     int count=0;
  168.  
  169.     int firstpoint=0;
  170.  
  171.    
  172.  
  173.     while (count<length) {
  174.  
  175.         /*Check if values within integration limits*/
  176.  
  177.         if (xvalues[count] <= uplim){
  178.  
  179.             if (xvalues[count] >= lowlim) {
  180.  
  181.                 if (firstpoint == 0) {
  182.  
  183.                     /*If the lower limit is not zero, add in the first part. If it is, this part will be zero anyway*/
  184.  
  185.                     if (count != 0) *integral += (xvalues[count]-lowlim)*(fvalues[count-1]);
  186.  
  187.                     firstpoint = 1;
  188.  
  189.                 }
  190.  
  191.                 else {
  192.  
  193.                     /*Add the next part of the integral*/
  194.  
  195.                     *integral += (xvalues[count]-xvalues[count-1])*(fvalues[count-1]);
  196.  
  197.                 }
  198.  
  199.             }
  200.  
  201.         }
  202.  
  203.         count++;
  204.  
  205.     }
  206.  
  207. }
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