1 files changed, 49 insertions, 0 deletions
diff --git a/macros/pchips.sci b/macros/pchips.sci
new file mode 100644
index 0000000..78c7473
--- /dev/null
+++ b/macros/pchips.sci
@@ -0,0 +1,49 @@
+function d = pchips(x,y,delta)
+
+
+   n = length(x);
+
+   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));
+ else
+
+   d(1) = ((2*h(1)+h(2))*delta(1) - h(1)*delta(2))/(h(1)+h(2));
+   if sign(d(1)) ~= sign(delta(1))
+      d(1) = 0;
+   elseif (sign(delta(1)) ~= sign(delta(2))) & (abs(d(1)) > abs(3*delta(1)))
+      d(1) = 3*delta(1);
+   end
+   d(n) = ((2*h(n-1)+h(n-2))*delta(n-1) - h(n-1)*delta(n-2))/(h(n-1)+h(n-2));
+   if sign(d(n)) ~= sign(delta(n-1))
+      d(n) = 0;
+   elseif (sign(delta(n-1)) ~= sign(delta(n-2))) & (abs(d(n)) > abs(3*delta(n-1)))
+      d(n) = 3*delta(n-1);
+   end
+   end
+   
+   
+   
+   
+   end
+   
+   endfunction