# Question:How to inverse interpolate a 2D lookup table in MapleSim?

## Question:How to inverse interpolate a 2D lookup table in MapleSim?

Dear Community,

I would like to have an inverse interpolation with a 2D lookup table in MapleSim. The usual 2D lookup interpolation has u1 column values, and u2 row values, and a corresponding   y   table values, i.e. y = f(u1,u2). Now I would like to go the reverse way. Suppose I know y, and u2, and I would like to get u1. How can I implement this in MapleSim? An additional information is, that the 3D surface represented by the f(u1, u2) function is a smooth, slightly curved, monotonically sloping surface, so to any  y  value a unique pair of u1 and u2 values belong.

With my specific data, which are attached in the TestVLP.xlsx file:

• u2 values are: 1st row, cells 2 .. 14
• u1 values are  1st column, rows 2 .. 11
• tabulated values are all the rest, i.e. from cell(2,2) .. cell(11,14)

Now for my case:

• u2 = 42000.0
• y   = 94.5614

How much is u1? I know the correct answer from elsewhere, it should be something very close to u1 ~ 85. This  y  value is in the rectangle bordered by columns 7 .. 8  and rows 5 .. 6 in the Excel file.

So my question is how do I correctly implement this in MapleSim? As visible from the attached TestInverse2DInterpolation.msim file I tried to do it with an Inverse Block Constraints component and a horizontally flipped 2D Lookup Table (VLP) and Constants for y and u2, but upon running MapleSim I get an error message that no solution is found, although the solution is relatively easy and straightforward. May I ask you to have a look at it, what can be the problem here, what do I do wrong? I’m using MapleSim 2019.2.

best regards

Andras

TestInverse2DInterpolation.msim

TestVLP.xlsx

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