[R] why function 'sum' within 'aggregate' need an 'index'?

Hi, people. I am using R-2.5.0 now, when tried the function aggregate with sum, it showed an error as following: a - gl(3,10) b - rnorm(30) aggregate(b,list(a),sum) # here is the error message, it complained that an error in FUN(X[[1L]], missing INDEX, and no defaults value. but the tapply

Re: [R] why function 'sum' within 'aggregate' need an 'index'?

On Mon, 2007-07-09 at 20:14 +0800, jingjiang yan wrote: Hi, people. I am using R-2.5.0 now, when tried the function aggregate with sum, it showed an error as following: a - gl(3,10) b - rnorm(30) aggregate(b,list(a),sum) # here is the error message, it complained that an error in