Plot curve through data points

Hi,

I am trying to plot a curve line through a set of points as showin in my drawing

I am using the following code to interpolate, but it is giving me the wrong graph.

x = [15.9, 16.9, 17.5, 19.6];
v = [1.108287307, 1.130052358, 1.118465615, 1.102750628];

xi = [x(1):0.0000001:x(end)];
vid=interp1(x,v,xi,'spline');
plot(x,v,'b*')
hold on
plot(xi,vid,'r')

Any help would be appreciated,

Thanks.

Answer 1

[the cyclist]

You can use a different interpolation method. pchip looks like what you want:

x = [15.9, 16.9, 17.5, 19.6];
v = [1.108287307, 1.130052358, 1.118465615, 1.102750628];

xi = [x(1):0.0000001:x(end)];
vid=interp1(x,v,xi,'pchip');

figure
plot(x,v,'b*')
hold on
plot(xi,vid,'r')

[Marcus Boyd]

That's brilliant, thanks very much