How to do Bankers Rounding in JMP

nathan-clark

I was recently asked about banker's rounding and didn't find anything in the JMP documentation. I wrote the quick function below (as well as a formula option), but was curious if 1) JMP has a canned method for doing banker's rounding and 2) what other/better methods may be useful vs. mine. http://wiki.c2.com/?BankersRounding 

bankerRound = Function( {inputValue},
	{inputValue, fDiff, cDiff, modX, bankRound},
	fDiff = inputValue - Floor( inputValue );
	cDiff = Ceiling( inputValue ) - inputValue;
	modX = Modulo( Round( inputValue, 0 ), 2 );
	If(
		cDiff == fDiff & modX == 0, bankRound = Ceiling( inputValue ),
		cDiff == fDiff & modX != 0, bankRound = Floor( inputValue ),
		bankRound = Round( inputValue, 0 )
	);
	Return( bankRound );
);
inputValue = Empty(); // put column name here 
fDiff = inputValue - Floor( inputValue );
cDiff = Ceiling( inputValue ) - inputValue;
modX = Modulo( Round( inputValue, 0 ), 2 );
If(
	cDiff == fDiff & modX == 0, bankRound = Ceiling( inputValue ),
	cDiff == fDiff & modX != 0, bankRound = Floor( inputValue ),
	bankRound = Round( inputValue, 0 )
);

ih

It is not built in but I think this accomplishes the same thing:

 

bankerRound = Function( {inputValue},
	if(	mod(inputValue, 0.5) == 0 & ! mod(inputValue, 1) == 0,
		round(inputValue / 2) * 2,
		round(inputValue)
	)
);

tests = { 0,0.499,0.5,0.501,1,1.499,1.5,1.501,2,2.499,
	2.5,2.501,3,3.499,3.5,3.501,-0.499,-0.5,-0.501,
	-1,-1.499,-1.5,-1.501,-2,-3};

for( i = 1, i <= N items( tests ), i++,
	Write( char( tests[i] ) || " -> " || 
		char( bankerRound( tests[i] ) ) || "\!N" );
);