diff options
Diffstat (limited to 'macros/pchips.sci')
| -rw-r--r-- | macros/pchips.sci | 37 |
1 files changed, 25 insertions, 12 deletions
diff --git a/macros/pchips.sci b/macros/pchips.sci index 78c7473..c639ca2 100644 --- a/macros/pchips.sci +++ b/macros/pchips.sci @@ -1,27 +1,40 @@ function d = pchips(x,y,delta) +//Piecewise Cubic Hermite Interpolating Polynomial (PCHIP) +//Parameters +// x: a vector +// y: is Y is vector then it must have the same length as x and Y is matrix then the last dimension of Y must equal +//length(X). +// delta: Points for interpolation +// d: vector of interpolantant at delta +//Examples: +//x = -3:3; +//y = [-1 -1 -1 0 1 1 1]; +//xq1 = -3:.01:3; +//v=pchips(x,y,xq1) +// n = length(x); - if n==2 + if n==2 d = repmat(delta(1),size(y)); - + else d = zeros(size(y)); - + k = find(sign(delta(1:n-2)).*sign(delta(2:n-1)) > 0); - + h = diff(x); hs = h(k)+h(k+1); w1 = (h(k)+hs)./(3*hs); w2 = (hs+h(k+1))./(3*hs); - + if ~isempty (k) then - - + + del_mx = max(abs(delta(k)), abs(delta(k+1))); del_mn = min(abs(delta(k)), abs(delta(k+1))); d(k+1) = del_mn./conj(w1.*(delta(k)./del_mx) + w2.*(delta(k+1)./del_mx)); @@ -40,10 +53,10 @@ function d = pchips(x,y,delta) d(n) = 3*delta(n-1); end end - - - - + + + + end - + endfunction |