title: Getting cumulative proportion in pca
body: <p>I want to retrive the cumulative proportion of explained variance after a pca in R. <code>summary(pca)</code> returns this result in its last row, but how can I extract this row?</p>
  
  <pre><code>summary(prcomp(USArrests, scale = TRUE))
  Importance of components:
                            PC1    PC2     PC3     PC4
  Standard deviation     1.5749 0.9949 0.59713 0.41645
  Proportion of Variance 0.6201 0.2474 0.08914 0.04336
  Cumulative Proportion  0.6201 0.8675 0.95664 1.00000
  </code></pre>
  
  <p>I tried <code>s &lt;- summary(prcomp(USArrests, scale = TRUE))</code>  and s[3] etc, but it doesn't return the last row. </p>