How would I make a dataset where each "site", "season", "year", and "species name" is completely crossed (every site was visited during each year/season, and each species could have been caught anytime and place -> i.e. 5 sites x 2 seasons x 2 years x 2 species = df size is 40×5).
df <- data.frame(site = rep(c("1", "2", "3", "4", "5"), each = 2),
season = rep(c("dry", "wet"), each = 10),
year = rep(c(2019, 2020), each = 10),
species_name = rep(c("Sailfin molly", "Hardhead silverside"), each = 10),
num = sample(x = 0:15, size = 20, replace = TRUE))
>Solution :
You could use the expand.grid() function:
library(tidyverse)
site <- c("1", "2", "3", "4", "5")
season <- c("dry", "wet")
year <- c(2019, 2020)
species_name <- c("Sailfin molly", "Hardhead silverside")
num <- sample(x = 0:15, size = 40, replace = TRUE)
df <- data.frame(expand.grid(site, season, year, species_name) %>% mutate(num = num))
colnames(df) <- c("site", "season", "year", "species_name", "num")