list(N= 12,
         Y = structure(
            .Data = c(1,1,
            1,-1,
            -1,1,
            -1, -1,
            2, NA,
            2, NA,
            -2, NA,
            -2, NA,
            NA, 2,
            NA, 2,
            NA, -2,
            NA, -2),
            .Dim = c(12, 2)))