LeastSquaresFit with Unit of Measure (Mathcad Prime 11.0)

Please include your worksheet, you may need to put it in a zip file.

Cheers

Terry

If you click on your LeastSquaresFit expression, go to the Calculations tab, and click on the Error Tracing arrows, where does the calculation trail lead back to?  Which expression does it point to?

Stuart

From what you show it looks like it should work OK, so the error may be in the parts you don't show. That's the values in Matrix M and most importantly the definition of your function Z₀. It may be that in some cases this function returns a dimensionless zero, while in other cases it returns a quantity with units. This can often work well, but in some cases it can lead to problems.
And then - error messages in Prime are not always accurate. The error does not necessarily have to do directly with the units.

I would therefore also recommend that you post your Prime sheet here. Either together with the data CSV file or with the data in a Matrix M that is already integrated in the Prime sheet (although this would be difficult to do in Prime).
Without the sheet, we can only grope in the dark and helplessly suggest one thing or another.
Apart from error tracing (which may refer to the Z₀ function) as suggested by Stuart, you could also try omitting the optional arguments in the LeastSquareFit function (i.e., the last two) and see if the problem persists (I guess it will).
Or you could try your luck with the genfit function.
genfit(x,y, ß, GW)=   should also give you a suitable value for ß.

It's only a guess, but your expression 

is looking for a set of values, one for each set of values of x and y.

Often with this error vectorizing the RHS will allow computation to succeed; an alternative would be to create a function and solve for each point.

The attached program demonstrates a least squared fit of data to a polynomial function.  It works without the LeastSquaresFit function and runs in Prime Express, (built in version 4).  

Since you haven't shared What your expression should look like you can try this on your data to get curves that fit polynomial functions of sigma.

Smarter people than I might be able to adapt this scheme to other function types.

Good luck.

Hi, working with dimensionless variables in all the worksheet, since the beginning, everything works:

However

and

Those errors lead back to

However

So I don't understand why "Those units are not compatible".

To provide the source code I need some time to clean it up.

Thanks