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This question already has an answer here:

To apply and visualize PCA in R often ggbiplot() is used. What is the meaning of this plot ? Why it is useful for PCA ?

We can consider this example: https://tgmstat.wordpress.com/2013/11/28/computing-and-visualizing-pca-in-r/

Figure

In particular, what is the meaning of arrows and circle?

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marked as duplicate by amoeba says Reinstate Monica, gung - Reinstate Monica r Sep 2 '16 at 0:00

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • $\begingroup$ Thanks for comments. I have seen the posts. I have understood that arrows are linked to correlation: more correlated are two variables and more collinear are the arrows. It is true? And what is the precise relation? $\endgroup$ – Ef_Ci Sep 1 '16 at 23:55
  • $\begingroup$ And what about the white circle? Thanks for your consideration! $\endgroup$ – Ef_Ci Sep 1 '16 at 23:56
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    $\begingroup$ You may also want to read Positioning the arrows on a PCA biplot. $\endgroup$ – gung - Reinstate Monica Sep 2 '16 at 0:03
  • $\begingroup$ I think you will find the information you need in the linked thread. Please read it. If it isn't what you want / you still have a question afterwards, come back here & edit your question to state what you learned & what you still need to know. Then we can provide the information you need without just duplicating material elsewhere that already didn't help you. $\endgroup$ – gung - Reinstate Monica Sep 2 '16 at 0:04
  • $\begingroup$ Regarding the white circle, see "Visualizing a million" thread: "The white circle indicates the theoretical maximum extent of the arrows." $\endgroup$ – amoeba says Reinstate Monica Sep 2 '16 at 9:20