topic Re: Custom Function - how to reference the column in Discussions

Custom Function - how to reference the column

hogi — Sun, 29 Oct 2023 22:20:20 GMT

It is cool that custom functions can be used as well as part of custom formulas in Formula Editor.

With the Transform Category command, the

New Custom Function( "myNamespace", "Add Ten", Function( {x, y = 10}, x + y ),  << Transform Category( "Custom" ));

from https://www.jmp.com/support/help/en/16.2/#page/jmp/create-custom-functions-transforms-and-formats.shtml

will show up in the right click New Formula Column Menu - and produce a column with formula

I just started with @txnelson 's approach
https://community.jmp.com/t5/Discussions/Formula-for-Number-of-Unique-Categories-in-Column/m-p/55284/highlight/true#M31262
to generate a column to Count Unique values - but instead of typing the formula, I wanted to use a Custom Function.

The manually generated Formula Column works, but the column that uses the Custom Function count unique doesn't.

It fails with the error message

Seems that x in the by() expression is not replaced with the column name.

So, use Eval(Substitute() to fix the issue?
... but how?

With

Eval(Substitute(Expr(Summarize( values = by( _col_ ) )),Expr(_col_),Name Expr(x) ));

I get

- because in a Column Formula :x is treated as :x[row()]. Argh ...

Along this line, I start to wonder why does this work:

[NB: the red zig-zag line just tells the user that print in a column formula is not a good idea]

why does Jmp know that it has to send get values to the COLUMN :sex and and not to :sex[row()].
And why does it actually return :sex[row()] in the second line - and not the column :sex ?

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

Add Custom Functions(
	New Custom Function(
		"custom",
		"count unique",
		Function( {x},
			As Constant( Summarize( values = by( x ) ) );
			N Items( values );
		),
		<<Transform Category( "Custom" ),
		<<Description( "count unique values" )
	)
);

New Column( "functionColumn",
	Formula(
		As Constant( Summarize( values = by( :sex ) ) );
		N Items( values );
	)
); //works

New Column( "customFunctionColumn", Formula( custom:count unique( :sex ) ) ); //doesn't work

Re: Custom Function - how to reference the column

yuichi_katsumur — Thu, 02 Nov 2023 04:59:33 GMT

Hello @hogi ,

I'm not sure if this is a smart approach, but the following script works. I used eval insert function. I hope it helps.

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

Add Custom Functions(
	New Custom Function(
		"custom",
		"count unique",
		Function( {x},
			Eval( Parse( Eval Insert( "As Constant( Summarize( values = by( :^x^ ) ) )" ) ) );
			N Items( values );
		),
		<<Transform Category( "Custom" ),
		<<Description( "count unique values" )
	)
);

New Column( "customFunctionColumn", Formula( custom:count unique( "sex" ) ) );

Re: Custom Function - how to reference the column

hogi — Thu, 02 Nov 2023 20:30:24 GMT

hm, unfortunately, it doesn't work:

produces the error message:

So, the same as like with

Substitute (..., Expr(_col_),Name Expr(x))

I guess it's because a function call to make it work has to be

custom:count unique( "sex" )

instead if

custom:count unique( :sex )

Re: Custom Function - how to reference the column

hogi — Sat, 04 Nov 2023 20:50:51 GMT

I just found an earlier (2018) version of the same question:

Re: Custom Function - how to reference the column

hogi — Mon, 06 Nov 2023 20:23:06 GMT

The quite definite reply from Jmp Support TS-00063463