[ always returns a huxtable, while $ and [[
return the underlying data.
For the replacement function [<-, if value is a huxtable, then its cell properties will be
copied into x. In addition, if value fills up an entire column, then column properties
will be copied into the replaced columns of x, and if it fills up an entire row, then
row properties will be copied into the replaced rows of x.
Replacement functions $<- and [[<- change the data without affecting any properties.