Completely agree with your point but my question is why there is a hint in training to use that particular system model and Lookup. Is it necessary to go as per hint if i can derive the same value using Yearvalue function.
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Just to expand on this a little. We often we this sort of construct using time formulas in modules dimensioned by Time and many other dimensions. It might be that you are using a subsidiary view, so the cell count is already optimised. As you might already know, we don't advocate Subsidiary views, unless by exception, and in this case, why are you doing the calculation in this module?. Do you have it repeated in another module? What if you or someone else in the future wants to build the same formula?; the formula will probably then be re-entered and worst case it wouldn't be set up as a subsidiary view.
So, I would still split the formula up and move it to a module dimensioned purely by time - that is the logical place for it, and conforms to PLANS
As this is only related by time, the effect will be marginal; it will increase the cell count slightly and hardly touch performance, but it is a good practice. The more you start modelling like this, the more you start thinking about the constructs of the formulae and where the component parts reside
Now, whenever you need to refer to the resulting formula, you point to the Time module - It has done the calculation once, and will only ever calculate once!
If you haven't already, please do look at the Planual as it outlines all things best practice
Cheers and happy modelling
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