Ree distrubution

    #include <stdio.h>
    #include <string.h>
    #include <math.h>
    // Initiallization routine for random number
    void   RandomInitialise(int,int);
    // Call to generate a random number between 0  and 1
    double RandomUniform(void);
    // Call to generate a Gaussian random number
    double RandomGaussian(double,double);
    // Call to generate a random integer between the two arguments
    int    RandomInt(int,int);
    // call to generate a random double between the two arguments
    double RandomDouble(double,double);
    FILE *ofp;
    int main ()
    {
      int i,j, r = 10000,Bin[10000], l, Reeint[10000], N =100;

      double theta,phi,pi=3.14159;
      double Rx[10000], Ry[10000], Rz[10000], b0=1.0, Ree[10000], temp=0, k=0.0, c=1, avgRee =0;

      // First need to initiallize the random number by giving it 2 seeds
      /* Initiallize the Random number by giving it 2 integers
         The integers should be between 0 and 31328 and 0 and 30081 */

      RandomInitialise(1802,9373);

     ofp=fopen("data9.txt","w");

      for(i=0;i<r;i++)
      {
              Rx[0]=0;
              Ry[0]=0;
              Rz[0]=0;
              temp=0;
             // printf("New walk is...\n");
              for(j=1;j<N+1;j++)
              {
                      theta = RandomDouble(0, 2*pi);
                      phi = RandomDouble(0,pi);
                      Rx[j] = Rx[j-1] + b0*cos(phi);
                      Ry[j] = Ry[j-1] + b0*sin(phi)*sin(theta);
                      Rz[j] = Rz[j-1] + b0*sin(phi)*cos(theta);



               //      printf("x = %f, y = %f, z = %f\n", Rx[j], Ry[j], Rz[j]);



              }

              Ree[i] = sqrt(Rx[N]*Rx[N] + Ry[N]*Ry[N] + Rz[N]*Rz[N]);
             // printf("Ree is = %f\n", Ree[i]);



              /*temp = Ree;
              Ree = Ree+temp;*/


      }
      for(i=0; i<N; i++)
              {

              avgRee = avgRee + Ree[i];

              }
                avgRee = avgRee/N;
            for(i=0; i<N; i++)
            {
                printf("Ree Value = %f\n", Ree[i]);
            //  fprintf(ofp,"%f\n",Ree[i]);


            }
              printf("Average Ree is %f\n", avgRee);

              fprintf(ofp,"Average Ree  = %f\n",avgRee);



    for(j=0; j<r;j++)
    {
        int tracker=0;
        for(i=0; i<r; i++)
        {
            if(Ree[i]>k && Ree[i]<c)
            {
                tracker++;
            }
        }
        k = k++;
        c = c++;
        Bin[j]=tracker;
    }
    for(i=0; i<r; i++)
    {
        printf("Bins are...%d\n", Bin[i]);
        fprintf(ofp,"%d\n",Bin[i]);

    }






      // Generate 2 random numbers (theta and pi)
      // theta is between 0 and 2PI and phi is between 0 and PI


     // printf("%f %f\n", theta, phi);

      // Now do the same but use the function RandomDouble

      theta = RandomDouble(0, 2*pi);
      phi = RandomDouble(0,pi);

     // printf("%f %f\n", theta, phi);



    }

    #define FALSE 0
    #define TRUE 1

    /*

     This Random Number Generator is based on the algorithm in a FORTRAN
     version published by George Marsaglia and Arif Zaman, Florida State

     University; ref.: see original comments below.

     At the fhw (Fachhochschule Wiesbaden, W.Germany), Dept. of Computer
     Science, we have written sources in further languages (C, Modula-2
     Turbo-Pascal(3.0, 5.0), Basic and Ada) to get exactly the same test
     results compared with the original FORTRAN version.
     April 1989
     Karl-L. Noell <NOELL@DWIFH1.BITNET>
     and  Helmut  Weber <WEBER@DWIFH1.BITNET>

     This random number generator originally appeared in "Toward a Universal
     Random Number Generator" by George Marsaglia and Arif Zaman.
     Florida State University Report: FSU-SCRI-87-50 (1987)
     It was later modified by F. James and published in "A Review of Pseudo-
     random Number Generators"

     THIS IS THE BEST KNOWN RANDOM NUMBER GENERATOR AVAILABLE.

     (However, a newly discovered technique can yield
     a period of 64^600. But that is still in the development stage.)
     It passes ALL of the tests for random number generators and has a period
     of 2^144, is completely portable (gives bit identical results on all
     machines with at least 24-bit mantissas in the floating point
     representation).

     The algorithm is a combination of a Fibonacci sequence (with lags of 97
     and 33, and operation "subtraction plus one, modulo one") and an
     "arithmetic sequence" (using subtraction).


     Use IJ = 1802 & KL = 9373 to test the random number generator. The
     subroutine RANMAR should be used to generate 20000 random numbers.
     Then display the next six random numbers generated multiplied by 4096*4096
     If the random number generator is working properly, the random numbers

     should be:

     6533892.0  14220222.0  7275067.0

     6172232.0  8354498.0   64633180.0

     */


    /* Globals */

    double u[97],c,cd,cm;

    int i97,j97;

    int test = FALSE;


    /*

     This is the initialization routine for the random number generator.
     NOTE: The seed variables can have values between:    0 <= IJ <= 31328
     0 <= KL <= 30081

     The random number sequences created by these two seeds are of sufficient
     length to complete an entire calculation with. For example, if sveral
     different groups are working on different parts of the same calculation,
     each group could be assigned its own IJ seed. This would leave each group
     with 30000 choices for the second seed. That is to say, this random
     number generator can create 900 million different subsequences -- with
     each subsequence having a length of approximately 64^30.

     */

    void RandomInitialise(int ij,int kl)

    {

            double s,t;

            int ii,i,j,k,l,jj,m;





            /*

             Handle the seed range errors

             First random number seed must be between 0 and 31328

             Second seed must have a value between 0 and 30081

             */

            if (ij < 0 || ij > 31328 || kl < 0 || kl > 30081) {

                    ij = 1802;

                    kl = 9373;

            }


            i = (ij / 177) % 177 + 2;

            j = (ij % 177)       + 2;

            k = (kl / 169) % 178 + 1;

            l = (kl % 169);


            for (ii=0; ii<97; ii++) {

                    s = 0.0;

                    t = 0.5;

                    for (jj=0; jj<24; jj++) {

                            m = (((i * j) % 179) * k) % 179;

                            i = j;

                            j = k;

                            k = m;

                            l = (53 * l + 1) % 169;

                            if (((l * m % 64)) >= 32)

                                    s += t;

                            t *= 0.5;

                    }

                    u[ii] = s;

            }


            c    = 362436.0 / 16777216.0;

            cd   = 7654321.0 / 16777216.0;

            cm   = 16777213.0 / 16777216.0;

            i97  = 97;

            j97  = 33;

            test = TRUE;

    }


    /*

     This is the random number generator proposed by George Marsaglia in

     Florida State University Report: FSU-SCRI-87-50

     */

    double RandomUniform(void)

    {

            double uni;


            /* Make sure the initialisation routine has been called */

            if (!test)

                    RandomInitialise(1802,9373);


            uni = u[i97-1] - u[j97-1];

            if (uni <= 0.0)

                    uni++;

            u[i97-1] = uni;

            i97--;

            if (i97 == 0)

                    i97 = 97;

            j97--;

            if (j97 == 0)

                    j97 = 97;

            c -= cd;

            if (c < 0.0)

                    c += cm;

            uni -= c;

            if (uni < 0.0)

                    uni++;


            return(uni);

    }


    /*

     ALGORITHM 712, COLLECTED ALGORITHMS FROM ACM.

     THIS WORK PUBLISHED IN TRANSACTIONS ON MATHEMATICAL SOFTWARE,

     VOL. 18, NO. 4, DECEMBER, 1992, PP. 434-435.

     The function returns a normally distributed pseudo-random number

     with a given mean and standard devaiation.  Calls are made to a

     function subprogram which must return independent random

     numbers uniform in the interval (0,1).

     The algorithm uses the ratio of uniforms method of A.J. Kinderman

     and J.F. Monahan augmented with quadratic bounding curves.

     */

    double RandomGaussian(double mean,double stddev)

    {

            double  q,u,v,x,y;


            /*

             Generate P = (u,v) uniform in rect. enclosing acceptance region

             Make sure that any random numbers <= 0 are rejected, since

             gaussian() requires uniforms > 0, but RandomUniform() delivers >= 0.

             */

            do {

                    u = RandomUniform();

                    v = RandomUniform();

                    if (u <= 0.0 || v <= 0.0) {

                            u = 1.0;

                            v = 1.0;

                    }

                    v = 1.7156 * (v - 0.5);


                    /*  Evaluate the quadratic form */

                    x = u - 0.449871;

                    y = fabs(v) + 0.386595;

                    q = x * x + y * (0.19600 * y - 0.25472 * x);


                    /* Accept P if inside inner ellipse */

                    if (q < 0.27597)

                            break;


                    /*  Reject P if outside outer ellipse, or outside acceptance region */

        } while ((q > 0.27846) || (v * v > -4.0 * log(u) * u * u));


        /*  Return ratio of P's coordinates as the normal deviate */

        return (mean + stddev * v / u);

    }


    /*

     Return random integer within a range, lower -> upper INCLUSIVE

     */

    int RandomInt(int lower,int upper)

    {

            return((int)(RandomUniform() * (upper - lower + 1)) + lower);

    }


    /*

     Return random float within a range, lower -> upper

     */

    double RandomDouble(double lower,double upper)

    {

            return((upper - lower) * RandomUniform() + lower);

    }