Re: How to downsample a vector?

Yoav Mor wrote: 
I was using downsample() and individual events in the data that are
important to me are lost (of course).

Which filter should I use? which one does matlab use when it plots?

Matlab just plots all the data that you sent to 'plot'. So if your screen is 1000 pixels wide and you have a 30000 numbers vector, then 30 successive numbers from you vector will be plotted onto the same column of pixels on your screen. Nothing is left out, no filtering is performed.

If you downsample your data, you'll probably loose information. In order to be sure, you should do a spectral analysis on your data. Then you can make an estimate how much you can downsample your data. If there are very sharp peaks in your data, then downsampling cannot be done without loosing information. No matter what downsample algorithm or filtering you choose...

The question remains though why you don't want to plot all data.

   Jeroen


Thank you.

Yoav.

daniel ennis wrote:


How are you "downscaling" the vector? Are you sub-sampling
dicretely
or are you filtering? There are a few ways to downsample.

Yoav Mor wrote:


Hi,

There's something I just don't get:

I need to plot a vector with 30,000-100,000 numbers.
The screen has around 1000 pixels in width.

When I downscale my vector to 1000, 2000 or even 4000, it still
doesn't look as good as it looked when I plotted the entire


vector.

What does matlab do? Does matlab use some downscaling 

interpolation

method? And for the most important question: How can I 

downscale

my

plot so it'll have as little data as possible but will still 

look

good?

Thank you!

Yoav. 
.

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