Question: what is pxx in matlab?
Answer: pxx = periodogram( x ) returns the periodogram power spectral density (PSD) estimate, pxx , of the input signal, x , found using a rectangular window. When x is a vector, it is treated as a single channel. ... If x is real-valued, pxx is a one-sided PSD estimate. If x is complex-valued, pxx is a two-sided PSD estimate.