Similar to aggregate. Splits the matrix into groups as
specified by groupings, which can be one or more variables. Aggregation
function will be applied to all columns in data, or as specified in formula.
Warning: groupings will be made dense if it is sparse, though data will not.
Usage
# S3 method for class 'Matrix'
aggregate(x, groupings = NULL, form = NULL, fun = "sum", ...)Arguments
- x
a
Matrixor matrix-like object- groupings
an object coercible to a group of factors defining the groups
- form
- fun
character string specifying the name of aggregation function to be applied to all columns in data. Currently "sum", "count", and "mean" are supported.
- ...
arguments to be passed to or from methods. Currently ignored
Value
A sparse Matrix. The rownames correspond to the values of the
groupings or the interactions of groupings joined by a _.
There is an attribute crosswalk that includes the groupings as a
data frame. This is necessary because it is not possible to include
character or data frame groupings in a sparse Matrix. If needed, one can
cbind(attr(x,"crosswalk"),x) to combine the groupings and the
aggregates.