Magnitude and Phase of Transformed Data
Important information about a transformed sequence includes its magnitude and phase. The MATLAB functions
angle calculate this information.
To try this, create a time vector
t, and use this vector to create a sequence
x consisting of two sinusoids at different frequencies.
Now use the
fft function to compute the DFT of the sequence. The code below calculates the magnitude and phase of the transformed sequence. It uses the
abs function to obtain the magnitude of the data, the
angle function to obtain the phase information, and
unwrap to remove phase jumps greater than
pi to their
Now create a frequency vector for the x-axis and plot the magnitude and phase.
The magnitude plot is perfectly symmetrical about the Nyquist frequency of 50 hertz. The useful information in the signal is found in the range 0 to 50 hertz.
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