It is useful to be able to simulate data with a specified structure. The faux package provides some functions to make this process easier. See the vignettes for more details.
You can install the released version of faux from CRAN with:
install.packages("faux")
And the development version from GitHub with:
# install.packages("devtools") devtools::install_github("debruine/faux")
between <- list(pet = c(cat = "Cat Owners", dog = "Dog Owners")) within <- list(time = c("morning", "noon", "evening", "night")) mu <- data.frame( cat = c(10, 12, 14, 16), dog = c(10, 15, 20, 25), row.names = within$time ) df <- sim_design(within, between, n = 100, mu = mu, sd = 5, r = .5)

p1 <- plot_design(df) p2 <- plot_design(df, "pet", "time") cowplot::plot_grid(p1, p2, nrow = 2, align = "v")

I started this project as a collection of functions I was writing to help with my own work. It’s one of many, many simulation packages in R; here are some others. I haven’t used most of them, so I can’t vouch for them, but if faux doesn’t meet your needs, one of these might.