Problem using interp1 cubic

2012 8 21
2 个回答
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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)

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Azzi Abdelmalek
Azzi Abdelmalek 2012-8-21
post your data
Jan
Jan 2012-8-21
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
Oleg Komarov 2012-8-21
@Alex: please use comments, do NOT create additional answers unless it is an answer to your problem.
Alex
Alex 2012-8-21
ok sorry
Oleg Komarov
Oleg Komarov 2012-8-21
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
Alex 2012-8-21
I try interp1(y1,x1,s,'cubic') but is the same image than jose's answer

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回答（2 个）

José-Luis
José-Luis 2012-8-21

2 个投票

Try inverting your x y data
interp1(x,y,...) to interp1(y,x,...)
Cheers!

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Jan
Jan 2012-8-21
Alex wrote: (Copied from Answer to the comment section:)
Don`t work
http://i684.photobucket.com/albums/vv208/Conde_Nefando/3.png
Jan
Jan 2012-8-21
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?!

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Titus Edelhofer
Titus Edelhofer 2012-8-21

1 个投票

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

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Titus Edelhofer
Titus Edelhofer 2012-8-21
I took another look at the image. The transpose should work, so ignore my answer ...
Alex
Alex 2012-8-21
编辑：Alex 2012-8-21
I transpose x1,y1 and when i do interp1 http://i684.photobucket.com/albums/vv208/Conde_Nefando/sd45452345.png
only a part work
Alex
Alex 2012-8-21
its works i need change s=[1:0.1:95] when i transpose x and y to s=[1:0.1:2152]

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Alex
Alex
2012-8-21

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