Faq how do manually calculate the limits for scores
Issue:
How do I manually calculate the limits for scores?
Possible Solutions:
Individual scores limits can be calculated using the code below, given a PCA model (modl
), the pc of interest (pc
), and the % confidence limit level desired (limitsvalue
):
>> pc = 2; %which PC to calculate limit for >> limitsvalue = 95; % confidence level (in %) >> L = modl.detail.ssq(pc,2); %get eigenvalue >> m = length(modl.detail.includ{1,1}); %get number of samples >> scorelimit = sqrt(L * tsqlim(m,1,limitsvalue));
To calculate scores limits for PCR models, the above must be slightly modified because the eigenvalues are stored in a different field. Replace the L = ...
line above with this:
>> L = modl.detail.pcassq(pc,2); %get PCR model eigenvalue
For PLS models, you must approximate L
(the eigenvalue) from the RMSE of the calibration data scores:
>> L = rmse(modl.loads{1,1}(:,pc)).^2; %estimate PLS model eigenvalue
This code assumes that no samples were excluded in the model. If any samples were excluded, use the modl.detail.includ{1}
field to calculate L
from only the included samples.
Notes:
To calculate limits for T2 and Q, see the related FAQ.
Still having problems? Please contact our helpdesk at helpdesk@eigenvector.com