I am trying to compile a program written in 'C' to draw a fractal using PGPlot, but I can't get it working.

This is the code I'm trying to compile:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <cpgplot.h>

/* ---------------------------------------------------------------------
* Plotting Julia set by the Level Set Method
*
* Usage on ULTRA:
* source /home/z/zrw/under/pgplot_c (set up just once a session)
* cc fractal1.c `cpgplot_link` -o fractal1 (to compile program)
*
* R. Willingale 2006-Feb-09
*----------------------------------------------------------------------
*/

/* maximum number of iterations for each point */
#define NITER 10000
/* number of columns in image */
#define NCOLS 800
/* number of rows in image */
#define NROWS 400

/* function to set colour table in pgplot */
void cpgsetlut();

int main

{
float rmin = -2.0, rmax = 2.0;
float pix=(rmax-rmin)/NCOLS;
float imin = -1.0, imax = imin+NROWS*pix;
double rtarget=1.e8, cr=-0.74543, ci=0.11301;
int i,j,ni;
float arr[NROWS*NCOLS], tr[6], zmin, zmax;
double rs,vr,vi,sr,si,tt;
zmin=NITER;
zmax=0.0;
for(i=0; i<NROWS; i++) {
si=imin+pix*(i+0.5);
for(j=0; j<NCOLS; j++) {
sr=rmin+pix*(j+0.5);
vr=sr;
vi=si;
rs=vr*vr+vi*vi;
ni=0;
while((rs<rtarget)&&(ni<NITER)) {

/* 4 lines to calculate the quadratic mapping missing */

tt = vr ;
vr = (vr*vr - vi*vi) + cr ;
vi = (2*tt*vi) + ci ;
rs = vr*vr + vi*vi ;

ni++;
}
tt=ni; tt=log(tt);
arr[j+i*NCOLS]=tt;
if(zmax<tt)
zmax=tt;
if(zmin>tt)
zmin=tt;
}
}
cpgbeg(0, "?", 1, 1);
cpgsetlut();
cpgwnad(rmin,rmax,imin,imax);
tr[0]=rmin-0.5*pix; tr[1]=pix; tr[2]=0.0;
tr[3]=imin-0.5*pix; tr[4]=0.0; tr[5]=pix;
cpgimag(arr,NCOLS,NROWS,1,NCOLS,1,NROWS,zmin,zmax,tr);
cpgbox("BCTN", 0.0, 0, "BCNST", 0.0, 0);
cpglab("real axis","imaginary axis","Julia set by the Level Set Method");
cpgend();
}

void cpgsetlut()
{
int i,icmin,icmax,n1,n2;
float dd, rcol,gcol,bcol;
cpgqcir(&icmin,&icmax);
dd=3.0/(icmax-icmin);
n1=icmin+(icmax-icmin)/3;
n2=icmin+((icmax-icmin)*2)/3;
for(i=icmin; i<icmax+1; i++) {
if(i<=n1) {
rcol=(i-icmin)*dd; gcol=0.0; bcol=0.0;
} else if((i>n1)&&(i<=n2)) {
rcol=1.0; gcol=(i-n1)*dd; bcol=0.0;
} else if(i>n2) {
rcol=1.0; gcol=1.0; bcol=(i-n2)*dd;
}
if(rcol>1.0) rcol=1.0; if(gcol>1.0) gcol=1.0; if(bcol>1.0) bcol=1.0;
cpgscr(i,rcol,gcol,bcol);
}
}

To compile the program I am using the command:

$ gcc -c fractal1original.c
$ f77 -o fractal1original fractal1original.o -lcpgplot -lpgplot -lgcc -lm

but it returns the error: /usr/lib/gcc/i486-linux-gnu/4.3.2/../../../../lib/libf2c.so: undefined reference to `MAIN__'

Really not sure how to go about solving this, the internet suggest its a problem linking the C libraries to the Fortran libraries.

Any help would be greatly appreciated.

Instead of
you probably want

Thanks for the quick reply, but unfortunately that didn't work, I still get the same error.

I've used a guide to try and get pgplot to work and I've had some success. I can run the precompiled demo that comes with pgplot however when I come to compile my own code I get a load errors about gfortran.

The guide I'm using can be found here:

http://www.dur.ac.uk/physics.astrolab/ppgplot.html

and here are the errors:

rob@rob-laptop:~/Desktop$ gcc -c fractal1original.crob@rob-laptop:~/Desktop$ f77 -o fractal1original fractal1original.o -lcpgplot -lpgplot -lX11 -lgcc -lm
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_concat_string'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_st_write_done'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_transfer_integer'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_st_read'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_st_inquire'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_stop_numeric'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_pow_i4_i4'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_st_write'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_getenv'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_st_read_done'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_runtime_error'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_compare_string'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_transfer_array'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_string_index'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_st_close'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_st_open'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_transfer_character'
/usr/local/lib/libpgplot.so: undefined reference to `_gfortran_os_error'
collect2: ld returned 1 exit status

I've also added: int MAIN__() {return 0;} to the code.