abs(x.^2)

Hello everyone

This was my code and i was trying to find peak power of the given sin signal.I dont understand how does it really work mathametically?

clc;f=1;

t=1/f;

x=1*sin(2*pi*f*t);

y=max (abs(x).^2);

[Martti Ilvesmäki]

.^2 is element-wise power function: https://se.mathworks.com/help/matlab/ref/power.html

abs() is absolute value and complex value function: https://se.mathworks.com/help/matlab/ref/abs.html?s_tid=doc_ta

x.^2 will raise all elements of vector or matrix x to the second power while abs() will take the absolute value of each element in vector or matrix. Using them both together in this case is unnecessary, because using x.^2 will remove all negative values already.

[Walter Roberson]

That is a formula for peak power, but not with that input. For it to work, the input has to be the fft of the signal (after subtracting the mean)

Your x only has a single sample.

That code with sin() looks like the bare outline of an attempt to calculate fft.

Answer 1

[Malar Vizhi]

Thankyou then what about this sir

y=mean(x.^2);

if x is array

[Martti Ilvesmäki]

The inner operation x.^2 (element-wise power) will be done first and next average of the result is calculated: https://se.mathworks.com/help/matlab/ref/mean.html

I highly recommend referring to Matlab documentation when you are using function you don't understand. The basic functions are well documented with examples and mathematical background included.

Also, please accept my first answer if you found it helpful to your original question. Thank you!

[Martti Ilvesmäki]

% Example
x = [1 2 3];
x_squared = x.^2; % --> [1 4 9]
x_squared_mean = mean(x_squared); % --> 4.6667

[Default]

This will fail for complex signals, the more accurate mean will be:

meanx = mean(abs(x).^2);

and the peak will be:

peakx = max(abs(x).^2);