Contributions incorrect in a continuous model with lags when selecting non-contiguous observations (Q893)
Contributions in SIMCA-online 15.0 are computed incorrectly for a continuous (non-batch) project that uses lags in the model.
This happens when:
- Selecting observations that are non-contiguous (not consecutive). For example: selecting observations 1 and 3, but not 2.
- Selecting two blocks of observations to compare them, if the first selected block is older (has earlier time stamps) than the second block. For example: selecting observation 1 first in one block, and then selecting observation 2 (resulting in that observation 1 is blue and observation 2 is red in the plot).
SIMCA-online doesn't include all data needed to be able to compute the values of the lagged variables, causing errors in the contributions.
If contributions are very important, SIMCA can be used to compute them: Use the Update SIMCA project functionality in SIMCA-online to add the relevant process data to the project file. Then you can predict this data in SIMCA (offline) with the original model, and finally create the contribution plot in SIMCA.
Note that you can still create contributions to average in SIMCA-online by selecting a single contiguous block of observations (no gaps in time). And you can still select two blocks of observations and create a contribution plot when the first block is more recent than the second block, and the blocks are contiguous (and next to each other).
SIMCA-online 15.0.1 includes a fix in the client so that erroneous contributions will never be displayed, but instead a small message is displayed alerting the user of the limitation.
The underlying cause will be fixed in a future version of SIMCA-online.