CrunchDataFrames are designed to mimic the ways that data.frames are used.
They should be a drop-in replacement in many places where data.frames are used.
# S3 method for CrunchDataFrame
dim(x)a CrunchDataFrame
CrunchDataFrames are generated not by downloading all of the variables from
a dataset, but rather only the variables that are needed by subsequent
functions. So, if you create a CrunchDataFrame, and then run a linear model
using lm(), only the variables used by the linear model will be downloaded.
CrunchDataFrames can be altered (that is: adding more columns, removing
columns, subsetting rows, etc.) with the same [, [[, and $ syntax as
data.frames.