`mkpp`

Builds a piecewise polynomial structure.

Syntax

pp = mkpp(breaks, coefs)

Creates the structure from the break points and one row of coefficients per interval.

pp = mkpp(breaks, coefs, d)

Creates a vector-valued piecewise polynomial with values of size d.

Description

Each row of coefs holds the polynomial for one interval, written in powers of the offset from the left break point: the row [a b c] on the interval starting at t means a*(x-t)^2 + b*(x-t) + c.

The structure is what spline, pchip and makima return when called without query points. Evaluate it with ppval and take it apart with unmkpp.

Input arguments

breaks: Vector of L+1 increasing break points that define L intervals.
coefs: Coefficients, one row per interval, highest power first, in the local variable x - breaks(i).
d: Optional size of the value at each point, for vector-valued functions.

Output arguments

pp: Structure with fields form, breaks, coefs, pieces, order and dim.

Example

Two quadratic pieces

pp = mkpp([0 1 2], [1 0 0; 2 1 0]);
ppval(pp, [0.5 1.5])
pp.order

Output

ans = 1×2

    0.2500    1.0000
ans = 3

mkpp