Dynamically Change Graph Builder Chart Type Depending on Variable Modeling Type

This recipe shows how to change the element type in Graph Builder dynamically, depending on whether the user selects a continuous or categorical x-axis variable in the Column Switcher. Elements are the graph types that appears as icons at the top of the Graph Builder palette. For continuous inputs, a radio button is added letting the user select between a Line of Fit and Contour. This recipe is useful when creating interactive charts for people who are not JMP experts and only need a limited number of options.

Ingredients:

Graph Builder
Expression Handling

Sample Data Table – Big Class Difficulty – Hard

Steps

Start with Names Default to Here(1) and open Big Class.

Names Default To Here( 1 );
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );

Create a function which sends a message to the Graph Builder platform that removes the existing element then adds a new one. It assumes that the Points element is already displayed and is element number 1, therefore the element to be removed is number 2.

// This function changes the type of chart being displayed.
// It takes a reference to a Graph Builder report (gbr) and the chart type required (gr)
// At the moment it assumes the Points element will always be included
changeElement = function( {gbr, gr},
	{default local},
	Eval(
		Substitute(
			Expr(
				gbr << remove element( 1, 1, 2 ) << add element( 1, 1, {Type( __aa__ ), X, Y} )
			), Expr( __aa__ ), gr
		)
	)
);

Create the new window which contains the column switcher (cs) to change the x-axis, a radio box (rb) to control the element type for continuous variables, and the Graph Builder (gb).

rb_out = "Line of Fit"; 
win1 = New Window( "Demo",
	Text Box(
		"Column switching between continuous and nominal variables will change line of fit to box plots",
		<<set wrap( 1000 )
	),
	H List Box(
		V List Box(
			cs = dt << column switcher( :height, {:age, :sex, :height} ),
			Outline Box( "Display option",
				Text Box( "Select option for continuous x-axis" ),
				rb = Radio Box( 
					{"Line of Fit", "Contour"}, 
					rb_out = rb << get selected();
					if( Column( dt, cs << get current ) << get modeling type == "Continuous",
						changeElement( Report( gb )[GraphBuilderBox( 1 )], rb_out ) 
					)
				)
			)
		),
		gb = dt << Graph Builder(
			Size( 534, 454 ),
			Show Control Panel( 0 ),
			Variables( X( :height ), Y( :weight ) ),
			Elements( Points( X, Y, Legend( 3 ) ), Line Of Fit( X, Y, Legend( 5 ) ) )
		)
	)
);

The column switcher is deliberately created outside the Graph Builder so we can later create a function to take action when the switcher changes.

Link the column switcher cs to the Graph Builder gb
```
cs << link platform( gb );
```

Create a Column Switch Handler. The function post is called by the handler once the change has been completed. The format comes directly from the Scripting Index.

post = Function( {previousColumn, currentColumn, switcher},
	gbr = Report( gb )[GraphBuilderBox( 1 )];
	If( Column( dt, cs << get current ) << get modeling type == "Continuous",
		changeElement( gbr, rb_out ),
		changeElement( gbr, "Box Plot" )
	);
);
cs << Make Column Switch Handler( 1, post );

Note that nothing needs to happen before the switch is completed, so the first argument of Make Column Switch Handler does nothing.

Finally, start the column switcher running for demo purposes.
```
cs << run();
```

Potential variation:

Create a "pre" change function which iterates over the existing elements in the Graph Builder (using << Get Elements), finds the one that needs to be removed and programmatically sets the third argument in << remove element (rather than relying on it being the second element).

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