This matlab program is for EEG signal, calculating PSD is a probability and statistical method, which is a measure of mean square value of random variables. Generally used in random vibration analysis, continuous transient response can only be described by probability distribution function, that is, the probability corresponding to a certain horizontal response. The power spectral density (PSD) is the statistical result of the response of the structure under random dynamic load excitation, and it is a relation curve between PSD value and frequency value