EEG signal PSD matlab question

hello every one

url=http://www.0zz0.com]**broken link removed**[/url]

this is my code for

using in matlab


pwelch(y1,window,[],[],1000) %Welch's method


which y1 is my EEG signal.

my sampling frequency is 1000Hz for the EEG signal,

I want to get a frequency range of 0-30Hz.but I'm getting from 0 to 500Hz.

I know it is something related to the sampling frequency so I what I need to do in order to get the 0-30 Hz frequency?? I can't change my sampling frequency since my original EEG sampling frequency is 1000Hz??

any idea

thanks

**broken link removed**

any help with that I need to understand what is the problem regarding this??

Your PSD is correct and by default it plots it to the half of the used sampling frequency. To only observe the region from 0 Hz to 30 Hz you need to re-set the axis of the figure.
To do this first check what is the number of the figure your PSD plot is drawn to. This can be seen in the top part of the plot-window (for me its Figure 2). You probably dont want to change the Y-axis so its better to first check what values are currently set to and use them when you input the new axis.

In matlab what you could do is this:

pwelch(y1,window,[],[],1000) %Welch's method
figure(2); % Makes the figure of the PSD plot active
h=axis; % Gets the current axis information
axis([0 30 h(3) h(4)]); % Sets the new axis 0-30 Hz on the x-axis and same y-axis as in the previous

type help axis for more info

hey can you please give me the code for eeg psd