HowToC:DrawPoints
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Drawing Points
Perhaps the most common object you will need to draw as a point. There are two different ways to do this, using either the PGPLOT-style functions or the native S2PLOT point functions.
For PGPLOT programmers, the functional interface to s2pt1 (draw a single point), s2pt (draw multiple points) and s2pnts (draw multiple points with different symbols) will seem very familiar. In each case, x, y and z coordinates are passed to the functions along with an integer value for the "marker" style to use.
Points example
Copy and paste the following code, and save the file as s2points.c
#include <stdio.h>
#include <stdlib.h>
#include "s2plot.h"
int main(int argc, char *argv[])
{
float xmin = -1, xmax = +1; /* X data range */
float ymin = -1, ymax = +1; /* Y data range */
float zmin = -1, zmax = +1; /* Z data range */
s2opend("/?",argc,argv); /* Which S2PLOT device to open? */
s2swin(xmin, xmax, ymin, ymax, zmin, zmax); /* Set the display coordinates */
s2pt1(0, 0, 0, 2);
float x[10], y[10],z[10]; /* Coordinates of points */
int sym[10]; /* Symbol to draw for each point */
int i;
for (i=0;i<10;i++) { /* Generate random point positions */
x[i] = drand48()*(xmax-xmin) + xmin;
y[i] = drand48()*(ymax-ymin) + ymin;
z[i] = drand48()*(zmax-zmin) + zmin;
}
s2pt(10, x, y, z, 1);
for (i=0;i<10;i++) { /* Generate more random point positions */
x[i] = drand48()*(xmax-xmin) + xmin;
y[i] = drand48()*(ymax-ymin) + ymin;
z[i] = drand48()*(zmax-zmin) + zmin;
sym[i] = random()%7; /* Choose a random symbol */
if (sym[i] == 3) sym[i] = 1; /* There is no symbol = 3 */
else if (sym[i] == 5) sym[i] = 6; /* There is no symbol = 5 */
}
s2pnts(10, x, y, z, sym, 10); /* Draw points with different symbols */
s2show(1); /* Hand over to the display */
return 1;
}
Compile using: cbuild.csh s2points<tt> and then run by typing <tt>s2points at the command prompt.
The obvious limitation with this example is that all of the points are the same colour! Point colours can be changed using the function s2sci. Put:
s2sci(N);
where N is an integer between 0 and 15 inclusive, before each of the point plotting commands. For a list of the default colour codes, see Colours.
Experiment for yourself
Try changing the number of points that are plotted, generate point positions by reading in your favourite dataset, or experiment with colours and markers.
Function Overview
For more information on the functions we have introduced so far, see:
Common Problems
Test code: s2points.c
This is the full test code for the point-drawing example.
Where to Next?
- Back to S2PLOT How To...
- Drawing lines
