What inputs for pcolor

Hi,

I am trying to generate a plot similar to this one:

I have a set of text files with two columns; Time in s and Velocity in m/s

I have a sampling freq of 20,000

I have generated a PSD using the code:

[Pxx, f] = pwelch(E,[],[],[],Fs);

where E is the all of the velocities and Fs is the sampling freq

How can I generate the above plot? What inputs should I put into the code:

pcolor(x,y,z)

Sizes:

E: 131072 1

f: 16385 1

Pxx: 16385 1

Sorry for the layout of the question, I dont understand enough to know how to ask the question eloquently

[darova]

What are your x,y,z? What do you want to plot? Can you attach your data?