How do I create a custom transform function that takes multiple columns as inputs?

BHarris

The scripting guide is pretty useful in describing how to make new custom transform functions, but it's not very clear on how to handle multiple columns.

 

How do I create a custom transform function that takes multiple columns as inputs?  E.g., if I select an X, a Y, and a Z columns and want to take the RSS (root-sum-squared) of those three columns?

 

Also, if the order matters, how is that order set?  Is it the order that the columns are selected in?

Mark_Bailey

I think that a Custom Function is a better choice for your case. The Custom Transform is restricted to a single input. The Custom Function is not restricted in this way.

 

funcDef = Function( {x, y, z}, Sqrt( Sum( x^2, y^2, z^2 ) ) );

description = "This function returns the root sum squared of three numbers.";

// examples can be multiple statements inside expr()
ex2 = Expr(
	dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
	Here:RSS( :age[1], :age[2], :age[3] );
);

parmHint1 = "x value";
parmHint2 = "y value";
parmHint3 = "z value";

/* create function using variables
the commands can also be accepted as arguments in New Custom Function */
newAdd = New Custom Function( "Here", "RSS", funcDef );

newAdd << Description( description );
newAdd << Prototype( "Here:RSS(x,y,z)" );
newAdd << Example( "Here:RSS(1,2,3)" );

// expr() Examples need to be passed inside NameExpr()
newAdd << Example( Name Expr( ex2 ) );
newAdd << Parameter( "Number", parmHint1 );
newAdd << Parameter( "Number", parmHint2 );
newAdd << Parameter( "Number", parmHint3 );

newAdd << Formula Category( "NumberStuff" );

// add myNamespace:Add Ten function to system
Add Custom Functions( newAdd );

 

The expression inside your function might include logic to address any need for proper order.