# interpolation

so i'm writing a program to do LaGrange interpolation. For those who aren't really familiar with the formulas for it, its like a series. I want to make this function into an array and for each value of the array have a certain formula plugged in, but I don't really know how to do it. The array is size n-1 (where n is inputted by the user as size). An example is

P(0)= (y-x1)/(x0-x1)
P(1)= (y-x0)/(x1-x0)
(where the user the xvalues are an entirely seperate array-that the user inputs- and y is input right before the array of P is declared)

hopefully this is straightforward..
any ideas?

## Comments

• : so i'm writing a program to do LaGrange interpolation. For those who
: aren't really familiar with the formulas for it, its like a series.
: I want to make this function into an array and for each value of the
: array have a certain formula plugged in, but I don't really know how
: to do it. The array is size n-1 (where n is inputted by the user as
: size). An example is
:
: P(0)= (y-x1)/(x0-x1)
: P(1)= (y-x0)/(x1-x0)
: (where the user the xvalues are an entirely seperate array-that the
: user inputs- and y is input right before the array of P is declared)
:
: hopefully this is straightforward..
: any ideas?

So you want to make an array of functions? In C this rather cumbersome to do, in C++ you can write a 'MyFunction' class:

[code]
struct MyFunction
{
double GetY(const double x);
double GetDerivative(const double x);
//etcetera
};
[/code]

I hope this will help you, at least to formulate the question even more straightforward.

See ya,
bilderbikkel
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