Arjen Markus (1 april 2011) When you want to illustrate a mathematical procedure, such as curve fitting, having a graph handy is quite useful. Here is a small program that allows you to change a parameter and see the immediate effect on the function. Not a major breakthrough in mathematical education perhaps, but it does show how easy it really is.
Some notes:
Here is a screen-shot:
# scale-plot.tcl -- # Demonstrate how a scale widget can interact with a plot # # Note: # Tested with an older version of Plotchart. Hence the # fiddling with the tags # package require Plotchart # refreshPlot -- # Draw a new line to fit the data # proc refreshPlot {p value} { # # Clean up the old line # (Still the only tag in this version of Plotchart) # .c delete data $p plot fit {} {} ;# Make a clean break # # The new line # for { set i 0 } { $i < 20 } { incr i } { set x [expr {-10.0 * ($i-10)}] set y [expr {$value * $x}] $p plot fit $x $y } } # # Set up the widgets # Note: # -from start at top # scale .s -from 10 -to -10 -variable param -resolution 0.1 -tickinterval 2 canvas .c -bg white -width 400 -height 300 grid .s .c -sticky news set p [::Plotchart::createXYPlot .c {-10 10 5} {-20 20 10}] # # Connect the plot to the scale widget # .s configure -command [list refreshPlot $p] # # Introduce some data # $p dataconfig measured -colour blue -symbol cross -type symbol $p plot measured 3.5 6.0 $p plot measured -2.5 -4.0 $p plot measured -1.5 0.05 $p plot measured 5. 4.05 # # Remove the tag "data" - we want to keep the measured points # .c dtag data data # # Dummy data point - error otherwise # $p plot fit 0.0 0.0