/* datagen.cpp * * This program creates a file name "sample.dat". * Three columns of data are generated. */ #include <stdio.h> #include <stdlib.h> #include <math.h> int main(int argc, char *argv[]) { int i; double x, y, z, ampl, phi; const double pi = 4.0*atan(1.0); FILE *fp; char *filename; filename = (argc<2? "sample.dat": argv[1]); printf("output file: %s\n",filename); fp = fopen(filename,"wt"); if (!fp) { printf("error opening output file\n"); return -1; } for (i=0; i<=500; i++) { x = 0.01*i; ampl = exp(-0.2*x); phi = 2.0*pi*x; y = ampl*cos(phi); z = ampl*sin(phi); fprintf(fp,"%g %g %g\n",x,y,z); } fclose(fp); return 0; }