## FAQ - Frequently Asked Questions

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### Issue:

How do I calculate my own T2 and Q limits?

### Possible Solutions:

Confidence limits for Q residuals (also known as "SPE") and Hotellings T2 can be calculated using the commands:
```   residuallimit
tsqlim```
To calculate new residual limits, you must pass the eigenvalues for the residuals from the model. Assuming you have a model structure named "model":
`qlimit = residuallimit(model.detail.reseig,cl);`
where `cl` is the confidence limit desired (in fractional confidence limit: 0.95 ). Note that for some model types, `.detail.reseig` is not defined. In these cases, you'll need to calculate the raw residuals themselves. You can usually do this with datahat, but you need to pass the original calibration data along with the model:
```   [xhat,residuals] = datahat(model,data);
qlimit = residuallimit(residuals,cl);```
To calculate new T2 limits, tsqlim can be called very simply:
`  tsqcl = tsqlim(m,pc,cl);`
where `m` is the number of samples in the model, `pc` is the number of PCs (or LVs) in the model, and `cl` is the confidence limit desired.

Note that tsqlim supplies the same result whether cl is a percent or fractional but residuallimit requires the a fraction cl.

To calculate limits for individual scores, see the related FAQ.

Still having problems? Check our documentation Wiki or try writing our helpdesk at helpdesk@eigenvector.com