Principal component analysis is a method of extracting important variables from a large set of variables

available in a data set.

I Have run PCA on Iris and plotted the scree plot which tells me to choose number of PC. but how many variable do I choose here from the given results of the PCA analysis pls let me know.

print(ir.pca)

Standard deviations:

[1] 1.7124583 0.9523797 0.3647029 0.1656840

Rotation:

PC1 PC2 PC3 PC4

Sepal.Length 0.5038236 -0.45499872 0.7088547 0.19147575

Sepal.Width -0.3023682 -0.88914419 -0.3311628 -0.09125405

Petal.Length 0.5767881 -0.03378802 -0.2192793 -0.78618732

Petal.Width 0.5674952 -0.03545628 -0.5829003 0.58044745

Importance of components:

PC1 PC2 PC3 PC4

Standard deviation 1.7125 0.9524 0.36470 0.16568

Proportion of Variance 0.7331 0.2268 0.03325 0.00686

Cumulative Proportion 0.7331 0.9599 0.99314 1.00000

insights much appreciated.

Regards,

tony