我正在使用 COZIGAM 包对物种的潜在分布进行建模。我有响应变量（“pb”，它告诉物种存在的位置）和预测变量（例如海拔、温度、降水等）。当我运行这个公式时：
# devtools::install_github('AndrewLJackson/COZIGAM')
coz.model <- cozigam(formula=pb ~ s(altitude) + s(combustible) + s(distribution) + s(e1) + s(e2) + s(e3) + s(euc.human) + s(euc.river) + s(fccarb) + s(fccmat) + s(forarb) + s(aspect) + s(slope) + s(precipitation) + s(radiation) + s(tipestr_class) + s(tipestr_forest) + s(tmean), data=sdmdata2, family=poisson)
它出现一个错误警告，即：
as.matrix(x) 中的错误：找不到对象“高度”
但是，当我运行时as.matrix(sdmdata2)，'altitude' 变量在我的矩阵中退出。的输出dput(head(sdmdata2))是：
structure(list(X = 1:6, pb = c(2L, 2L, 2L, 2L, 2L, 2L), altitude = c(879L,
1094L, 1035L, 410L, 342L, 665L), combustible = c(6L, 6L, 3L,
0L, 3L, 3L), distribution = c(6L, 6L, 6L, 0L, 6L, 0L), e1 = c(4L,
4L, 2L, 0L, 4L, 0L), e2 = c(0L, 0L, 2L, 0L, 2L, 0L), e3 = c(0L,
0L, 4L, 0L, 2L, 0L), euc.human = c(790.569397, 3201.562012, 1750,
250, 250, 1952.562012), euc.river = c(0, 4069.705078, 353.5534058,
1030.776001, 559.0170288, 0), fccarb = c(90L, 70L, 40L, 0L, 30L,
0L), fccmat = c(5L, 10L, 35L, 0L, 60L, 80L), forarb = c(1L, 1L,
2L, 0L, 5L, 0L), aspect = c(6L, 8L, 6L, 4L, 3L, 3L), slope = c(5L,
3L, 5L, 2L, 6L, 5L), precipitation = c(87.01500702, 79.57628632,
81.86239624, 75.10630798, 49.58106995, 69.55927277), radiation = c(160.1408997,
163.4971008, 161.8542938, 157.9179993, 159.2113953, 160.6203003
), tipestr_class = c(1L, 1L, 1L, 7L, 1L, 2L), tipestr_forest = c(6L,
6L, 6L, 0L, 6L, 0L), tmean = c(141.7760925, 134.9530029, 141.9192047,
171.9972992, 186.2566986, 157.0391998)), .Names = c("X", "pb",
"altitude", "combustible", "distribution", "e1", "e2", "e3", "euc.human",
"euc.river", "fccarb", "fccmat", "forarb", "aspect", "slope",
"precipitation", "radiation", "tipestr_class", "tipestr_forest",
"tmean"), row.names = c(NA, 6L), class = "data.frame")
有人知道是什么问题吗？