hELLO!
I want to use a PCA with a dataset of 17 variables (congeners)
measured in 120 food and air samples.
The concentrations are expressed in
different units of measurement (ng/Nm3, ng/kg)
Is it correct assign to each
variable a value that corrispond to the concentration measured for the
congener, reported in relation to the sum of the 17 congener concentrations?
I
use the covariance matrix in PCA, with this output:
--------------------------------------------------------------------------
Component | Eigenvalue Difference Proportion Cumulative
-------------+------------------------------------------------------------
Comp1 | .0474947 .0380502 0.6869 0.6869
Comp2 | .00944454 .00531611 0.1366 0.8234
Comp3 | .00412843 .000944856 0.0597 0.8831
Comp4 | .00318357 .00184526 0.0460 0.9292
Comp5 | .00133831 .000309329 0.0194 0.9485
Comp6 | .00102898 .000329951 0.0149 0.9634
Comp7 | .00069903 .000190709 0.0101 0.9735
Comp8 | .000508321 .00011746 0.0074 0.9809
Comp9 | .000390861 .0000988767 0.0057 0.9865
Comp10 | .000291985 .000103161 0.0042 0.9908
Comp11 | .000188823 .0000422023 0.0027 0.9935
Comp12 | .000146621 .0000242402 0.0021 0.9956
Comp13 | .000122381 .0000341471 0.0018 0.9974
Comp14 | .0000882337 .0000235538 0.0013 0.9986
Comp15 | .0000646799 .0000359076 0.0009 0.9996
Comp16 | .0000287723 .0000287712 0.0004 1.0000
Comp17 | 1.03334e-09 . 0.0000 1.0000
--------------------------------------------------------------------------
2 principal components accounted for a total of 82% of variance in the data set
Is it correct?
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