multiple periodograms

I have some data in vector 'x'. I can compute a periodogram easily enough by

y=x;
[Pxx,w] = pwelch(y);

Great, all is good, BUT if I want to transform 'x' to absolute values and compute the periodogram for this as well, like

y=(x);
y2=abs(x);
[Pxx,w] = pwelch(y);
[Pxx,w] = pwelch(y2);

Well does not really work, I am just re-writing [Pxx,w] !

so I try like

y=(x);
y2=abs(x);
[Pxx,w] = pwelch(y);
[2Pxx,2w] = pwelch(y2);

But then I have a syntax error as [2Pxx,2w] is not allowed, I must use 'Pxx' and 'w'.

How can I this?

Answer 1

[Wayne King]

Just do

    [Pxx2,w] = pwelch(y2);

Or any legal variable name. MATLAB variable names must start with a letter followed by up to 30 letters, digits, or underscores. It is also case sensitive.

[john birt]

thank you