How to outline a curve

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dj
dj on 12 Oct 2014
Commented: dj on 13 Oct 2014
Hello.
If I'm trying to plot variables x and y, and the y values vary so much that the curve looks like the following: http://i.stack.imgur.com/4uiNT.png
The only difference is that mine is a single curve of data with a lot of noise. Is there a way I could just plot the upper and the lower curves so I could just look at the boundaries? Do I have to use the findpeak command?
Thank you for your time!
  2 Comments
pietro
pietro on 12 Oct 2014
How could you make that plot from the boundary array?
dj
dj on 13 Oct 2014
It's just an image that looks like my plot. I just have a really noisy data ):

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Accepted Answer

Mohammad Abouali
Mohammad Abouali on 12 Oct 2014
Edited: Mohammad Abouali on 12 Oct 2014
  3 Comments
Mohammad Abouali
Mohammad Abouali on 12 Oct 2014
Edited: Mohammad Abouali on 12 Oct 2014
There is no two sets of data. In this graph there is only 1 set, i.e. the blue line. Once you run the HANTS algorithm you have three options, Lo (which gives you the red line) Hi (which gives you the black line), or none which gives you the green line.
You might need to play a bit with the sampling and frequency numbers to get a proper fit.
This function is generally for smoothing the data set and also removing outliers. Of course it gives the main frequency in your data set and you can use it for harmonic analysis.
dj
dj on 12 Oct 2014
I'll look more into this and see if I can figure it out. Thank you for your help!

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More Answers (1)

John D'Errico
John D'Errico on 12 Oct 2014
I suppose you could use my SLM tools . It has an option to fit an envelope curve, so you could first fit the infimum curve, then the supremum curve to get lower and upper bounds from a pair of calls.
You might want other options in the total prescription, but a start might be...
LBcurve = slmengine(x,y,'envelope','inf');
UBcurve = slmengine(x,y,'envelope','sup');
  1 Comment
dj
dj on 12 Oct 2014
Edited: dj on 12 Oct 2014
Hi, thank you for the feedback!
I've tried using your program on two different computers, and it's giving me an error of the following:
Error using diag Out of memory. Type HELP MEMORY for your options.
Error in slmengine>slmengine_cubic (line 2316) rs = diag(1./sum(abs(Mineq),2));
Error in slmengine (line 255) slm = slmengine_cubic(x,yhat,prescriptionhat);
Could this be because the data is too large? It consists of over 550000 set of points... I'm really new to Matlab, so any help would be appreciated (:

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