HOW TO PLOT DATES FROM A FILE WITH GTKPLOT??

Hi everyone!!
I need to plot dates from a file using gtk_plot.
As i saw in examples, dates are gdouble format.
So this is my code to read the dates:
#define N_P 3

void main()

{
     FILE *fp,*fp_sal;
     char registro[200][N_P];
     int i;
         
     gdouble px[N_P],py[N_P];
         fp=fopen("c:\\devcpp_fin\\datos\\datos.txt","r");
     fp_sal=fopen("c:\\devcpp_fin\\datos\\salida.txt","w");
     for(i=0;i<N_P;i++)
     {
         fgets(registro[i],200,fp);
         sscanf(registro[i],"%lg %lg",&px[i],&py[i]); 
         fprintf(fp_sal,"%lg\n",&px[i]);
     }                 
     
}

The problem is that doesn't write good px[i]!!
so...what's the format error??

thanks a lot!
}     


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