Question

aggregate function works fine

aggregate(weight ~ feed, data = chickwts, mean)
       feed   weight
1    casein 323.5833
2 horsebean 160.2000
3   linseed 218.7500
4  meatmeal 276.9091
5   soybean 246.4286
6 sunflower 328.9167

But after loading library(memisc) in R 2.14.1, the same code produces the following error

Error in `[.default`(xj, i) : invalid subscript type 'closure'

What is the problem and how to solve this? Thanks in advance for your help.

Answer 1

This package redefines the aggregate method.
There is often a warning in those cases, but since aggregate.formula is a hidden method, there is no warning.
You can explicitely use the initial aggregate function by specifying its namespace
(three colons are needed because it is a hidden method).

stats:::aggregate.formula(weight ~ feed, data = chickwts, mean)