S4 classes, some help with the basics

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?

     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 at i)  ### I know this doesn't work, but this is the
question... what grammar could I use?

}

################

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 at 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



---
XKCD<http://www.xkcd.com>

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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?

     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 at i)  ### I know this doesn't work, but this is the
question... what grammar could I use?
}

################

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 at 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



---
XKCD<http://www.xkcd.com>

	[[alternative HTML version deleted]]