pls package - validation

Hi,




I'm trying to fit PLSR model in R with 'pls' package with 22 samples (16 
train, 6 test). I know that basic for considering of number of component is 
cross-validation (in my case 'LOO') and then I should choose number of 
component with minimum of RMSEP (or first minimum). But problem is that 
values of RMSEP is increasing (not the opposite). Should I choose only 1 
component?




And then I tried compute R2 with my test-dataset (6 samples) and I received 
nonsensical values (below 0, bigger then 1).

Do you have any idea what may be caused? If it's my problem with fitting or 
problem with datasets.




Below, you can see my results:

pH.spec<-plsr(pH ~ spec, data=soil.train, validation="LOO")

summary(pH.spec)

Data: ??? X dimension: 16 501 
??? Y dimension: 16 1
Fit method: kernelpls
Number of components considered: 14

VALIDATION: RMSEP
Cross-validated using 16 leave-one-out segments.
?????? (Intercept)? 1 comps? 2 comps? 3 comps? 4 comps? 5 comps? 6 comps? 7 
comps? 8 comps? 9 comps? 10 comps? 11 comps
CV????????? 0.5343?? 0.5435?? 0.5506??? 1.629??? 1.617??? 1.742??? 1.921??? 
1.979??? 1.977??? 1.971???? 1.972???? 1.972
adjCV?????? 0.5343?? 0.5419?? 0.5486??? 1.587??? 1.570??? 1.688??? 1.860??? 
1.916??? 1.914??? 1.908???? 1.910???? 1.909
?????? 12 comps? 13 comps? 14 comps
CV??????? 1.972???? 1.972???? 1.972
adjCV???? 1.909???? 1.909???? 1.909

TRAINING: % variance explained
??? 1 comps? 2 comps? 3 comps? 4 comps? 5 comps? 6 comps? 7 comps? 8 comps? 
9 comps? 10 comps? 11 comps? 12 comps
X??? 96.410?? 99.655??? 99.87??? 99.90??? 99.93??? 99.94??? 99.95??? 99.96??
? 99.96???? 99.97???? 99.98???? 99.99
pH??? 3.649??? 8.342??? 19.41??? 67.48??? 88.96??? 97.19??? 99.69??? 99.94??
? 99.99??? 100.00??? 100.00??? 100.00
??? 13 comps? 14 comps
X????? 99.99?????? 100
pH??? 100.00?????? 100

R2(pH.spec, newdata = soil.test)

(Intercept)????? 1 comps????? 2 comps????? 3 comps????? 4 comps????? 5 comps
????? 6 comps????? 7 comps????? 8 comps? 
?? -1.65763???? -0.60849???? -0.05253???? -0.72870???? -2.84718???? -2.34102
???? -3.28201???? -3.68611???? -3.69817? 
??? 9 comps???? 10 comps???? 11 comps???? 12 comps???? 13 comps???? 14 comps
? 
?? -3.77271???? -3.74585???? -3.76342???? -3.76074???? -3.76110???? -3.76115
? 





Thank you in advance for your help






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