...
PCs | Batch | Center | Day | Month | Year | Amount | Concentr. | Row | Column | Stage | Grade | Age |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | 0.7905 | 0.0001809 | 6.9e-01 | 8.4e-01 | 8.2e-01 | 6.4e-01 | 9.7e-02 | 9.9e-01 | 1.2e-05 | 0.41 | 0.53 | 0.6716 |
2 | 1 | 0.7522 | 1.00 | 1.00 | 0.96 | 0.93 | 0.75 | 0.96 | 0.46 | 0.36 | 0.30 | 0.02475 |
3 | 1 | 0.03907 | 1.00 | 1.00 | 0.93 | 0.97 | 0.52 | 1.00 | 0.17 | 0.30 | 0.27 | 0.1425 |
Now remove the batch, plate row and plate column, look at the percent variance explained: 
Now the first principal component explains a little less than 15% of the overall variability. Correlation with the adjustment and bio variables, see if the center effect still present: