Problem using interp1 cubic

I`m trying to inter a grapich but it`s wrong im using interp1 cubic

How should be

It looks wrong

Help.

Edit [21 Aug 2012, 12:45 BST - OK] Added Alex's answer here

x1=[ 1.0000 6.1000 10.1800 135.3000 136.5750....86.7650 83.2800]
y1=[ 1 23 40...... 2144 2152]
s=[1:0.1:95]
z=interp1(x1,y1,s,'cubic')
plot(s,z)

[Azzi Abdelmalek]

post your data

[Jan]

How could we find out, what is wrong with the command you have used to create the wrong diagram without seeing the code? A suggestion for improvements must be based on wild guessing.

[Oleg Komarov]

@Alex: please use comments, do NOT create additional answers unless it is an answer to your problem.

[Alex]

ok sorry

[Oleg Komarov]

I think the problem is that it's not a function, i.e. you have multiple Ys for an X.

As Jose pointed out you might transpose the x with the y, interpolate and then re-transpose back.

[Alex]

I try interp1(y1,x1,s,'cubic') but is the same image than jose's answer

Answer 1

[José-Luis]

Try inverting your x y data

interp1(x,y,...) to interp1(y,x,...)

Cheers!

[Jan]

Alex wrote: (Copied from Answer to the comment section:)

Don`t work

http://i684.photobucket.com/albums/vv208/Conde_Nefando/3.png

[Jan]

Posting the problem and further explanations by picture only is not efficient. We cannot reproduce your diagrams when you do not provide the data. Perhaps only your drawing method fails?!

Answer 2

[Titus Edelhofer]

Hi,

the plot shows that it's not a function y = f(x) and also not a function x = g(y). So you will need to move to a 2D parametrization. Take a look at the function spline that can handle the case of an arbitrary trajectory in the plane, e.g. take a look at example 4 (the cirlce).

Titus

[Titus Edelhofer]

I took another look at the image. The transpose should work, so ignore my answer ...

[Alex]

I transpose x1,y1 and when i do interp1 http://i684.photobucket.com/albums/vv208/Conde_Nefando/sd45452345.png

only a part work

[Alex]

its works i need change s=[1:0.1:95] when i transpose x and y to s=[1:0.1:2152]