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Partial Autocorrelation

Explore the concept of partial autocorrelation to understand the direct relationships between lagged observations in a time series. Learn how to interpret partial autocorrelation coefficients, differentiate them from autocorrelation, and apply tools like the statsmodels plot_pacf function to graph and analyze partial autocorrelation for effective time series modeling.

The partial autocorrelation coefficient

The partial autocorrelation coefficient λj\lambda_j of a time series yty_t measures the linear relationship between observations that are jj periods apart, once the effect of all observations in between has been accounted for. In other words, λj\lambda_j tells us how strong the impact that ytjy_{t-j} has on yty_t after subtracting the impact that observations ytj+1,ytj+2,...,yt1y_{t-j+1}, y_{t-j+2}, ..., y_{t-1} ...