playing BLT

JM The following examples show the basic usage of the BLT charting capabilities.

As many of the BLT users will notice, these examples just show the tip of the iceberg, but sometimes we are looking for the minimal example for a quick startup...


Barchart basic usage

package require BLT
blt::barchart .g -title "Comparison"
pack .g
.g element create BT1 -xdata {1 2 3 4 5 6 7 8} -ydata {.76 .98 .88 .92 .96 .98 .91 .80} \
        -label {Series 1} -showvalues y

Barchart showing two series of data

package require BLT
blt::barchart .g -title "Comparison" -barmode aligned
pack .g
.g element create BT1 -xdata {1 2 3 4 5 6 7 8} -ydata {.76 .98 .88 .92 .96 .98 .91 .80} \
        -label "Series 1" -showvalues y
.g element create BT2 -xdata {1 2 3 4 5 6 7 8} -ydata {.1 .2 .3 .4 .5 .6 .7 .8} \
        -label "Series 2" -showvalues y -foreground red

Function plotting using [vector expr ...]

UK:

#!/usr/bin/wish
 
package require BLT
namespace import ::blt::*
 
proc compute args {
    catch {
        ::y expr {                      \
              ($::a * (::x ^ 3))  + ($::b * (::x ^ 2))   \
            + ($::c * ::x)        +  $::d                \
        }
    } cerr 
}
 
label .l -text "Function: ax^3 + bx^2 + cx + d"        ; table . .l 0,0
 
graph .g -width 700 -height 600 -bd 2 -relief groove   ; table . .g 1,0 -fill both
Blt_ZoomStack .g

vector ::x ; ::x seq -10 10 0.5
vector ::y
 
set items {label variable to from digits resolution tickinterval gridpos}
set scale_cfg {
    a ::a  -0.31  0.3 5 0.001 0.1   1,1
    b ::b  -1.01  1.0 5 0.002 0.5   1,2
    c ::c  -4.01  4.0 4 0.01  2.0   1,3
    d ::d -10.01 10.0 3 0.1   5.0   1,4
}
foreach $items  $scale_cfg {
    set $variable 0.0
    trace variable $variable w compute

    set w .sc$label
    set label [ string totitle $label ]
    scale $w -label $label \
            -variable $variable -to $to -from $from \
            -digits $digits -resolution $resolution \
            -tickinterval $tickinterval \
            -bd 2 -relief groove
    table . $w $gridpos -fill y
}
 
# fill vector ::y 
compute
 
.g element create Function -xdata ::x -ydata ::y -pixels 3
.g axis configure y -min -20 -max 20
.g grid configure -hide no -dashes { 2 2 }
 
# ready

See also: Tclodbc + BLT