Doug Jenkins wrote:

ALGLIBNewbie - I don't have time to look at the C++ version, but it seems to work in VBA. One thing is that it seems that M (number of functions) needs to be an even number, so try your code with M = 4 or 6!

Thank you very much, Doug! Indeed the

*number of functions* set to an even number makes my code run. Boy, I can't believe days went by with all it needed was setting "5" to "6".

Okay, this means I can

*address *now the

**spline1dfithermite** function of ALGLIB. On to the next step, that is the maths. Again, I have no clue whether

**spline1dfithermite **is actually the function that suits my mathematical problem. To recap: My only input is 56 x-values and corresponding 56 f(x)-values. I need a math function that displays the curve just as Excel does. I suspect the form of the function to be something like

**f(x) = [ax^5 + bx^4] + cx^3 + dx^2 + ex + f**. Means, I actually only need the coefficients a, b, c, d, e and f calculated.

So now where I get some results from

**spline1dfithermite **I give it a try to hopefully do that.

The obvious main return object is

**spline1dinterpolant**.

**Code:**

struct spline1dinterpolant

{

bool periodic;

int n;

int k;

ap::real_1d_array x;

ap::real_1d_array c;

};

I set the

*number of functions M* which I learned must be an even number to 6. And after executing

**spline1dfithermite **with my 56 x/y data columns

**spline1dinterpolant **supplies these values:

**ap::real_1d_array c** delivers:

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**ap::real_1d_array c** delivers:

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**n** is 4,

**k** is 3, and

**periodic** is false.

And I have only but one more question and we're done: What does all this mean? Is

**c** the list of coefficients? That would be great.

Doug Jenkins wrote:

GetSplineData is my VBA routine to convert the input variant arrays into the correct form for the AlgLib VBA routines.

I studied your VBA code briefly. I can somewhat read what's going on but the mathematical background fails me.

One final remark: I could be light years away from the solution. But please don't give up on me, hahaha... I think it will be most valuable to the LIB-forum if you math pros keep giving a hand to absolute outsiders.