[R] Accessing the elements of summary(prcomp(USArrests))

[Erik Iverson]

Josh B wrote:
> Hello again,
> 
> I was hoping one of you could help me with this problem. Consider the
> sample data from R:
> 
>> summary(prcomp(USArrests))
> Importance of components: PC1     PC2    PC3     PC4 Standard
> deviation     83.732 14.2124 6.4894 2.48279 Proportion of Variance
> 0.966  0.0278 0.0058 0.00085 Cumulative Proportion   0.966  0.9933
> 0.9991 1.00000
> 
> How do I access the information contained within this summary? For
> instance, let's say I wanted to make a graph based on the second row
> ("Proportion of Variance").
> 

The easiest way is to use the ?str function to see how an object is put 
together.

So, assign the results of the summary to a variable

x <- summary(prcomp(USArrests))

then

str(x)

will lead you to :

plot(x$importance[2, ], type = "l")