Solution 3.6 - Chemometrics: Data Analysis for the Laboratory and Chemical Plant

1. The scores of the first four PCs (from bottom to top) are plotted against sample time.

2. PC1 shows some evidence of cyclicity because there appear to be a reoccuring pattern, however this is not very clear, probably because the pattern is also influenced by noise.

3. The correlogram is as follows.

4. It appears that there is a cyclicity with a frequency of around 6 datapoints, with maxima at points 7, 13 and 19. This cyclicity is emphasized because correlograms reduce the influence of correlated (non-stationary) noise allow the underlying cyclical trends to become more prominent.