What exactly is an dgCMatrix-class. There are so many attributes.

You should not really have worry about the internal structure of such a
thing - just treat it like a matrix.  E.g.,

train$data[1:3,1:3] # dots mean 0's

3 x 3 sparse Matrix of class "dgCMatrix"
     cap-shape=bell cap-shape=conical cap-shape=convex
[1,]              .                 .                1
[2,]              .                 .                1
[3,]              1                 .                .

dim(train$data)

[1] 6513  126

p <- train$data %*% matrix(1:126, ncol=1)
dim(p)

[1] 6513    1


If that doesn't work in some situation, convert it to a matrix with
as.matrix.

To see the details, in R, type
   class?dgCMatrix
or
   help("dgCMatrix-class")
In a browser seach window type
   R dgCmatrix
You should not have to make use of those details in your code.


Bill Dunlap
TIBCO Software
wdunlap tibco.com

Dear R list,

I came across dgCMatrix. I believe this class is associated with sparse
matrix.

I see there are 8 attributes to train$data, I am confused why are there so
many, some are vectors, what do they do?

Here's the R code:

library(xgboost)
data(agaricus.train, package='xgboost')
data(agaricus.test, package='xgboost')
train <- agaricus.train
test <- agaricus.test
attributes(train$data)

Where is the data, is it in $p, $i, or $x?

Thank you very much!

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