abs

Signal Processing Toolbox

Absolute value (magnitude).

y = abs(x)

Description

y = abs(x)

returns the absolute value of the elements of x. If x is complex, abs returns the complex modulus (magnitude):

abs(x) = sqrt(real(x).^2 + imag(x).^2)

If x is a MATLAB string, abs returns the numeric values of the ASCII characters in the string. The display format of the string changes; the internal representation does not.

This function is part of the standard MATLAB environment.

Example

Calculate the magnitude of the FFT of a sequence:

t = (0:99)/100;                      % time vector
x = sin(2*pi*15*t) + sin(2*pi*40*t); % signal
y = fft(x);                          % compute DFT of x
m = abs(y);                          % magnitude

Plot the magnitude:

f = (0:length(y)-1)'/length(y)*100;  % frequency vector
plot(f,m)