A computer implemented method for displaying values for an output variable
comprising displaying a first user interface element configured to
present values of a first input variable; displaying a second user
interface element configured to present values of a second input
variable; displaying a third user interface element configured to present
values of an output variable, the output variable varying in dependence
upon the first and second input variables; receiving first user input of
a value for the first variable via the first user interface element;
receiving second user input of a value for the second variable via the
second user interface element; and updating the third user interface
element to indicate at least one value of the output variable in response
to the first user input and the second user input.
