[Scilab-users] 3D interpolation : comments adding

[paul.carrico at free.fr]

Hi All

To go further in 2D/3D interpolation as I started in my previous emails,
I built the example here after. 

As suggested, I had a look to 
- cshep2d but but seems can not be used here (dimensions issue) 
- splin2d + interp2d 

In the later case, Am I right to say that splin2d "cross-sections" the
surface in order to define the "best spline" passing through the nodes
(in the cross section obviously), then the interpolation/calculation is
basically using this new 2D function, right ? 

if so this is not a linear interpolation between 2 nodes (as I expect),
isn't it? 

Paul 

############################################ 

mode(0)

n=10;
x = linspace(0,300,(n+1))';    // abscissa
t = [0 25 100];                         // temperature
z = 20*rand((n+1),3);            // ordinate
// Nota : we must have the same number of data for both x and z

//  plot3d
clf()
a=get("current_axes");
a.x_label; x_label=a.x_label; x_label.text=" X abscissa";
a.y_label; y_label=a.y_label; y_label.text=" Temperature T";
a.z_label; z_label=a.z_label; z_label.text=" y ordinate";
plot3d(x,t,z)

// Nota: if I do a cross section normal to XoZ plane, I've the basic
curve z=f(x,T)) -> seems correct

//  interpolation
xp = [22 103 236]'
tp = [5 56 85]'

[Xp,Tp] = ndgrid(xp,tp)
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