Re: Simulating data smoothing on a 2D matrix. New to Octave/Matlab platforms

[Søren Hauberg]

ons, 01 07 2009 kl. 10:48 +0100, skrev Nuno Santos:
> Søren Hauberg wrote:
> > tir, 30 06 2009 kl. 17:37 +0100, skrev Nuno Santos:
> >   
> >> First I would like to see the 2D matrix drawn on a 3D graphic, where 
> >> each value of the 2D matrix is a Z value on the 3D graphic.
> >>     
> >
> > Try the 'mesh' or 'surf' functions for such plots. For larger matrices,
> > you might consider just showing them as an image using 'imshow'. This
> > can be much faster, and it often provides a better overview.
> >   
> To draw using the mesh function I need 3 matrixes. The things is that I 
> only have one matrix and so, I need two other matrixes for X and Y to 
> make the Z have the point in the right place.
> 
> Isn't there a direct form of doing this? Or isn't there a way of 
> generating the other two matrixes automaticly?

You can omit the 'X' and 'Y' matrices, i.e. just call 'mesh (Z)' (same
goes for 'surf'). If you actually want the 'X' and 'Y' matrices, you can
use the 'meshgrid' function.

> >> Then I would like to apply several smoothing function (and if anyone 
> >> could point me some functions), to the data in order to visually see the 
> >> results.
> >>     
> I was looking for function to smooth noise variations from direct ADC 
> readings. I have found savgol filters on the internet so I was wondering 
> if octave had some similar filters

From
http://research.microsoft.com/en-us/um/people/jckrumm/savgol/savgol.htm
it sounds like these are just linear filters (I only read the first
couple of lines), so you can implement them using the 'conv2' function.
The link also provides some Matlab code that I guess should work
out-of-the-box in Octave.

I would still recommend looking at the 'imsmooth' function. It provides
several methods that you can easily use (both linear and nonlinear
stuff).

Søren