On 08/08/2011 8:04 PM, Mike Williamson wrote:
Hi All,
I have tried to find an answer within documentation, but I cannot:
o How can call a class "slot" without knowing the name a priori?
See ?slot.
E.g., let's say I use the "pcaMethods" library to create a "pcaRes"
object. How can I call parts of that object without using the specific
names of the object in the call?
example code:
library(pcaMethods)
myMatrix<- matrix(runif(1e4), ncol=100) ## silly, but sufficient for
example
myPCA<- pca(myMatrix) ## creates a "pcaRes" S4 class
for (i in slotNames(myPCA) ) {
summary(myPCA@i) ### I know this doesn't work, but this is the
question... what grammar could I use?
summary(slot(myPCA, i))
Duncan Murdoch
}
################
I would like to be able to print out the summary for each of the components
of the class "pcaRes" without knowing a priori the names of those
components. I could, for example in the above case, type in
summary(myPCA@completeObs) to get a summary of the input matrix. But I HAVE
TO TYPE "@completeObs". In the non-S4 world, I could type myPCA[[i]] for
lists, where "i" could be looping through either the list names, or the list
indices. Similarly, I could type myPCA[i] for arrays, where "i" again can
be either a numeric index or the name.
Without this ability to identify portions within an array / loop context, it
becomes exceedingly difficult to work in "S4 land". How is this sort of
thing done?
Thank you!
Mike
---
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