Graph Builder - adding interactive reference lines

[#1]

When using graph builder, it allows you to "highlight" or "select" a specific data subset within the legend. The corresponding output on the graph builder and data table will also highlight themselves. When a subset of data is selected, the other subsets fade into the background or increase their transparency in an interactive manner.

Can I have add reference lines that correspond to a selected data set behave interactively in the same way? And can I have these lines automatically color themselves as they do when I drop a nominal column into the legend field?

[#2]

Here's some starter JSL.

dt = Open( "$SAMPLE_DATA/Big Class.jmp" );

oldselection = [];// don't update when nothing changes by comparing old to new

f = Function( {a}, // this callback tells which points are changing selected state
	// and may send between 1 and N row numbers in the matrix a. 
	// this example will ignore a and just ask the table about the range of the currently
	// selected points.
	{subset, hmin, hmax, wmin, wmax, newselection}, // local variables
	newselection = dt << getselectedrows; // compare to previous selection...
	If( Try( N Rows( newselection ) != N Rows( oldselection ) | Any( newselection != oldselection ), 1 ),
		oldselection = newselection; // remember the new selection for next time
		dtSubset = dt << subset( SelctedRows( 1 ), LinkToOriginalDataTable( 1 ), invisible ); // make a subset of the selection to summarize
		dtSummary = dtSubset << Summary( Min( :height ), Min( :weight ), Max( :height ), Max( :weight ), Freq( "None" ), Weight( "None" ) );
		Close( dtSubset, "nosave" ); // done with the subset, use the summary...
		hmin = dtSummary:name( "Min(Height)" )[1]; // capture the range of the selected axis
		hmax = dtSummary:name( "Max(Height)" )[1];
		wmin = dtSummary:name( "Min(Weight)" )[1];
		wmax = dtSummary:name( "Max(Weight)" )[1];
		Close( dtSummary, "nosave" ); // done with the summary, use the captured values...
		// remove 2 old reflines first, from each axis, then add 2 new ones
		// remove the old ref lines from the weight axis (1==horizontal)
		Report( gb )[axisbox( 1 )] << removerefline( (Report( gb )[axisbox( 1 )] << getscript)["addrefline"] );
		Report( gb )[axisbox( 1 )] << removerefline( (Report( gb )[axisbox( 1 )] << getscript)["addrefline"] );
		// remove the old ref lines from the height axis (2==vertical)
		Report( gb )[axisbox( 2 )] << removerefline( (Report( gb )[axisbox( 2 )] << getscript)["addrefline"] );
		Report( gb )[axisbox( 2 )] << removerefline( (Report( gb )[axisbox( 2 )] << getscript)["addrefline"] );
		// add the new ref lines...extend the bounding box by .5 for the integer height/weight (not required)
		Report( gb )[axisbox( 1 )] << addrefline( wmin - .5, "solid", "red", "a", 2 );
		Report( gb )[axisbox( 1 )] << addrefline( wmax + .5, "solid", "green", "b", 2 );
		Report( gb )[axisbox( 2 )] << addrefline( hmin - .5, "solid", "blue", "c", 1 );
		Report( gb )[axisbox( 2 )] << addrefline( hmax + .5, "solid", "black", "d", 1 );

	);
);

rs = dt << make row state handler( f );

gb = Graph Builder(
	Size( 416, 300 ),
	Show Control Panel( 0 ),
	Show Legend( 0 ),
	Variables( X( :weight ), Y( :height ) ),
	Elements( Points( X, Y, Legend( 3 ) ) ),
	SendToReport( Dispatch( {}, "Graph Builder", OutlineBox, {Set Title( "" )} ), Dispatch( {}, "graph title", TextEditBox, {Set Text( "Demo" )} ) )
);

The JSL installs a RowState handler function in the data table; that function is notified when the table's row state data changes (when a row is selected/hidden/excluded, or the marker style or color changes.) The function calculates the min and max values of the selected columns and removes old ref lines and adds new ref lines.

The a-b-c-d ref lines are interactively tracking the rectangular point selection

It flashes as it updates because the display redraws when each refline is added or removed; it may get too slow with large data that takes too long to redraw the graph.

[#3]

Indexing the list via 

["addrefline"] 

- nice trick

Why does it work?

It finds the first Symbol (independent of upper/lower case & spaces) - and returns the first argument?

[#4]

Yes. Not well documented, but very useful with modal dialog <<ReturnResult. It is a sequential search, not as good as an associative array. comments in Modal Dialogs  2/5 down from top.

axisbox<<getscript returns a list of function-call-like elements, and as you point out (I just noticed too) only the first value can be retrieved.

Sorry, that JSL deserved better comments!