set.seed(8)
gros.degat <- data.frame(id = 1:4,
                         trt = sample(rep(c('controle', 'culture'), each = 2)),
                         zooplancton.T1 = runif(4),
                         poisson.T1 = runif(4),
                         zooplancton.T2 = runif(4),
                         poisson.T2 = runif(4))
  id      trt zooplancton.T1 poisson.T1 zooplancton.T2  poisson.T2
1  1 controle      0.3215092 0.76914695      0.4323914 0.001301721
2  2 controle      0.7189275 0.64449114      0.5449621 0.264458864
3  3  culture      0.2908734 0.45704489      0.1382243 0.276532247
4  4  culture      0.9322698 0.08930101      0.9278123 0.521107042