** Summary **

[ulis], 2003-03-12:

A little script to plot a graph on a [canvas]. Non-stop scrolling
capable. Can be used for real-time plotting.

[http://perso.wanadoo.fr/maurice.ulis/tcl/plot.gif]


** See Also **

   [A Graph plotter]:   a different approach.
   [Histogram Plotter]:   
   [Fun with functions]:   
   [Plotting data]:   


** Code **

======
#! /bin/env tclsh

package require Tk

# --------------------------
#   params
# --------------------------
# title
# canvas width & height
# delay between plots
# x = f(t)
# plot expression
# initial & final times
# accuracy
array set params {
    title     {sin(x)}
    width     400
    height    240
    delay     50
    x         {$t / 50.}
    plot      {sin($x)}
    t0        0
    #         {t1 < t0: non-stop scrolling}
    t1        -1
    accuracy  1.e-2
}

# --------------------------
#   plotting
# --------------------------
# computed heights
set h $params(height)
set h1 [expr {int($h * 0.5)}]  ;# canvas mid-height
set h2 [expr {$h1 + 1}]
set h3 [expr {int($h * 0.4)}]  ;# graph mid-height
# canvas & bindings
canvas .c -width $params(width) -height $h \
    -xscrollincrement 1 -bg beige
bind . <Destroy> { exit }
# plotting
wm title . $params(title)
bind .c <Configure> {
    bind .c <Configure> {}
    .c xview scroll $params(t0) unit
    set t $params(t0)
    set loop {
        if {$t != $params(t1)} {
            set x [expr $params(x)]
            set vv [expr $params(plot)]
            set v [expr {int($vv * $h3) + $h1}]
            if {abs($vv) < $params(accuracy)} \
            { 
                .c create text $t 0 -anchor n -text $t -fill gray
                .c create line $t 0 $t $h -fill gray
            }
            .c create line $t $h1 $t $h2 -fill gray
            .c create rectangle $t $v $t $v
            incr t
            if {$t > $params(width)} { .c xview scroll 1 unit }
            after $params(delay) [list if 1 $loop]
        }
    }
    after idle [list if 1 $loop]
}

pack .c
======

** Another set of parameters **

[http://perso.wanadoo.fr/maurice.ulis/tcl/plot2.gif]

======
array set params \
{
    title     {x^3 - x}
    width     400
    height    240
    delay     50
    x         {$t / 100.0}
    plot      {pow($x,3) - $x}
    t0        -200
    t1        200
    accuracy  1.e-6
}
======


<<categories>> Example | GUI | Plotting | Widget