Nik - rather than using a variable number of inputs (and so outputs), why don't you just have a single input parameter that is an nx3 array. Your output would then be a nx2 array. For example,
function [dataOut] = trg (dataIn)
n = size(dataIn,1);
dataOut = zeros(n,2);
for k=1:n
A1 = dataIn(k,1);
A2 = dataIn(k,2);
A3 = dataIn(k,3);
a=input('Value= ');
dataOut(k,:) = [(A2-A1)*a+A1,A3-(A3-A2)*a];
end
If you then call the above as
>> trg([1 2 3;0 2.5 5])
ans =
1 3
0 5
you get the expected answer.
