[R] Create design matrix

Justin Haynes jtor14 at gmail.com
Thu Nov 3 19:23:18 CET 2011


> expand.grid(c("M","F"),c("Y","O"))
  Var1 Var2
1    M    Y
2    F    Y
3    M    O
4    F    O


On Thu, Nov 3, 2011 at 10:56 AM, Bond, Stephen <Stephen.Bond at cibc.com> wrote:
> Greetings useRs,
> What is the easiest way to create a design matrix of several factor variables? Function gendata in Design seems to do that for a fitted model, but how to do that only on several factor vectors??
> The result should be a df with one row for each distinct combination of levels of factors eg for (M,F) (Y,O)
> We get
> M Y
> M O
> F Y
> F O
> In reality I will have more than 1000 rows so doing by hand not good.
> Maybe there is a way with "outer", but I couldn't see it.
> All the best to everybody.
> Stephen
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