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Using etfe and spa commands

idwtyidwty Posts: 1Member
I believe the general form of these commands are as follows:


where dat is the matrix that contains the input and output data
where fv is some final value of the number of frequency partition (I think)
where g and h is just some dummy variable
where linspace means it'll be using linear rather than logarithm
where [] denotes the default

I believe fv means how many points you want for the frequency response Bode plot (e.g. resolution). But when I tried it out I found out well its not exactly like that.

I did several tests, using a fv = 400:1:410, I found out that even though a change of 1 value the Bode plot changes drastically. And this is NOT a resolution change (e.g. the amount of details).

Another test that I did was using a fv = 500:500:2000, I found that it actually have a resolution change. The general form of the Bode plot is the same except more detailed peaks; specifically peaking lower and lower near the last point. For example, say fv = 500 had the last and lowest point at -2000. Then fv = 2000 would have had something like -6000.

I really do not know why this is happening or how to choose the "correct" fv value. I tried using ident (system identification tool) to find what I should be expecting but that did not help much.

The following is the code for the script (m-file) I used.
t1rm = temperature1 with mean removed (output)
s1rm = steam value position1 with mean removed (input)


for i=1:fv-1
hold on

for i=1:fv-1

title('Frequency Response (Zero-Mean)')

for i=1:fv-1
hold on

xlabel('Frequency (Rads/s)')
ylabel('Phase (Deg)')

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