Bonjour, Si on considère un exemple un peu étendu : data3 <- structure(list(code_parcelle = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L), .Label = c("12ENICA08001", "12ENICA08002"), class = "factor"), date = structure(c(1L, 2L, 3L, 7L, 1L, 2L, 5L, 4L, 6L), .Label = c("2013-05-06", "2013-0...