[Gnuplot-info] linespoints with sparse points

[K.Moriyama <km...@mb...>]

Hi.

I wonder why this feature has not included in gnuplot so far.
when you plot several lines (e.g. calc. results) at once, 
it may be hard to distinguish them, especially on a monochrome
terminal or hard copy.

many other tools (e.g. kaleida graph) has a feature with which
you can plot lines with points sparsely put along the lines,
so that you can easily distinguish the lines.

  ------*-------*-------*-----*-------
  ------o-------o-------o-----o-------

gnuplot's "linespoints" puts all the points, like 

  ************************************
  oooooooooooooooooooooooooooooooooooo

then, i added a new feature to specify the number of points which
is skipped when plotting by "linespoints".
(lines are drawn by all the data)
"pointskip" is the magic word.

usage:  plot "data" with linespints pointskip 50
        plot "data" wi linesp pointsk 50
        plot "data" wi lp psk 50

this plots a line and sparse (every 50) points along it.
it works only for 2d plots. it takes effect with "linespoints" or 
"points".

i bet this kind of feature definitely makes many people happier.

see the patch below. (dirty?) 

k.moriyama

--------8<----------------8<----------------8<--------
--- term_api.h.org	2004-07-29 16:22:30.000000000 +0900
+++ term_api.h	2004-07-29 16:24:10.000000000 +0900
@@ -69,6 +69,7 @@
     int     pointflag;		/* 0 if points not used, otherwise 1 */
     int     l_type;
     int	    p_type;
+    int     p_skip;      /* skip interval for linespoints km040729 */
     double  l_width;
     double  p_size;
 #ifdef PM3D
--- misc.c.org	2004-07-29 16:22:40.000000000 +0900
+++ misc.c	2004-07-29 16:32:44.000000000 +0900
@@ -731,6 +731,7 @@
 	lp->pointflag = allow_point;
 	lp->p_type = def_point;
 	lp->p_size = pointsize;	/* as in "set pointsize" */
+        lp->p_skip = 1;  /* no-skip by default  km040729 */
 	while (!END_OF_COMMAND) {
 	    if (almost_equals(c_token, "linet$ype") || equals(c_token, "lt")) {
 		if (set_lt++)
@@ -800,6 +801,20 @@
 		continue;
 	    }
 
+	/* parse pointskip or psk   km040729 */
+	    if (almost_equals(c_token, "pointsk$ip") || equals(c_token, "psk")) {
+		if (allow_point) {
+		    c_token++;
+		    lp->p_skip = real(const_express(&t));
+		    if (lp->p_size < 1)
+			lp->p_size = 1;
+		} else {
+		    int_warn(c_token, "No pointskip specifier allowed, here");
+		    c_token += 2;
+		}
+		continue;
+	    }
+
 	    /* unknown option catched -> quit the while(1) loop */
 	    break;
 	}
@@ -1004,7 +1019,7 @@
 		arrow->head_lengthunit = hsize.scalex;
 		arrow->head_angle = hsize.y;
 		arrow->head_backangle = hsize.z;
-		/* invalid backangle --> default of 90.0− */
+		/* invalid backangle --> default of 90.0− */
 		if (arrow->head_backangle <= arrow->head_angle)
 		    arrow->head_backangle = 90.0;
 		continue;

--- graphics.c.org	2004-07-29 16:57:52.000000000 +0900
+++ graphics.c	2004-07-29 17:05:16.000000000 +0900
@@ -2670,16 +2670,38 @@
     int i;
     int x, y;
     struct termentry *t = term;
+/* point skipping function   km040729 */
+    int count;
 
+    count = 0;
+    for (i = 0; i < plot->p_count; i++) {
+        count++;
+        if (count < plot->lp_properties.p_skip ) {
+           continue;
+        } else {
+           count = 0;
+ 	   if (plot->points[i].type == INRANGE) {
+	       x = map_x(plot->points[i].x);
+	       y = map_y(plot->points[i].y);
+	       /* do clipping if necessary */
+	       if (!clip_points || (x >= xleft + p_width && 
+			y >= ybot + p_height && x <= xright - p_width && 
+			y <= ytop - p_height))
+		   (*t->point) (x, y, plot->lp_properties.p_type);
+           }
+	}   
+    }
+/*
     for (i = 0; i < plot->p_count; i++) {
 	if (plot->points[i].type == INRANGE) {
 	    x = map_x(plot->points[i].x);
 	    y = map_y(plot->points[i].y);
-	    /* do clipping if necessary */
+	    /* do clipping if necessary * /
 	    if (!clip_points || (x >= xleft + p_width && y >= ybot + p_height && x <= xright - p_width && y <= ytop - p_height))
 		(*t->point) (x, y, plot->lp_properties.p_type);
 	}
     }
+*/
 }
 
 /* plot_dots: