Re: [Gnuplot-info] Plot one additional point, manually

[Thomas S. <t.s...@fz...>]

Allan Felipe <allanfelipebr <at> yahoo.com.br> writes:

> 
> 
> Hi, I would like to plot a set of points which is being generated by a C
> code, using pipe. It would plot a sequence of these points making a video.
> Here is an example that does the job:
> 
> ----------------------------------------------------------------
> 
> #include <stdio.h>
> #include <stdlib.h>
> #include <unistd.h>
> 
> int main() {
> 
>     FILE *pipe;
>     pipe = popen("gnuplot -persist", "w");
> 
>     fprintf(pipe, "set xlabel 'x (m)' \n");
>     fprintf(pipe, "set ylabel 'y (m)' \n");
>     fprintf(pipe, "set pointsize 1 \n");
>     fprintf(pipe, "set xrange[-0.1:4.1] \n");
>     fprintf(pipe, "set yrange[-0.1:4.1] \n");
> 
>     int i;
>     double x, y;
> 
>     for (i = 1; i < 30; i++) {
>         x = (double) rand() / RAND_MAX;
>         y = (double) rand() / RAND_MAX;
> 
>         fprintf(pipe, "plot '< echo %lf, %lf' w p pt 7 lc -1 notitle \n",
> 4*x, 4*y);
> 
>         fflush(pipe);
>         usleep(150000);
>     }
> 
>     fclose(pipe);
>     return 0;
> }
> 
>
--------------------------------------------------------------------------------
> 
> It works ... however, the way it is done, it plots just one point at a time.
> I would like to plot one point, then another one, but keeping the last point
> ... then another, keeping all the other 2 ... so I'd like to know how I
> could add one point to a graph that is already done, that would solve my
> problem.

maybe the 'replot' command helps:

for (i = 0; i<  30; i++) {
   x = (double) rand() / RAND_MAX;
   y = (double) rand() / RAND_MAX;
   if (i) {
      fprintf(pipe,
         "replot '<  echo %lf, %lf' w p pt 7 lc -1 notitle \n",
         4*x, 4*y);
   } else {
      fprintf(pipe,
         "plot '<  echo %lf, %lf' w p pt 7 lc -1 notitle \n",
         4*x, 4*y);
   }
   fflush(pipe);
   usleep(150000);
}