08. Time Series Analysis
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What is PACF
Partial Auto Correlation Function - shows only direct linkages i.e. day 7 is directly affected by day 0
What is ACF
Auto Correlation Function - shows the indirect linkages i.e. day 1 is indirectly affected by day 0. and each day onto the next.
What is fanovarience
An increasing spread of the data but around a constant mean
What are the four parts of a decomposed time series
Trend - steady underlying long term trend Seasonal - regular repeating pattern over time Cyclic - also a periodic fluctuation but over lengthy periods ie Boom and Bust Random - white noise
What is the box-jenkins methodology
Condition the Data - check and make it stationary & see if there is seasonality Estimate the model parameters - PACF & ACF Run Diagnostics (repeat potentially)
What is covariance in time series
Two time series mirror (or do the reverse for a negative covariance) each other
What is autocorrelation ACF
Indirect relationship. This is the moving average - how one point is related to the next point (or a number of points over a wider range).
What is partial autocorrelation PACF
Direct relationship. This is where something happens on days x days away from a day which manifests later. Autoregressive