我找不到 rpart 对象中节点的拆分值(或其他数据)。我在 summary(sample_model) 中看到它，但不在列表或数据框中
一些示例数据
foo.df <- structure(list(type = c("fudai", "fudai", "fudai", "fudai", "fudai",
"fudai", "fudai", "tozama", "fudai", "fudai", "tozama", "tozama",
"fudai", "tozama", "fudai", "fudai", "tozama", "fudai", "fudai",
"tozama", "fudai", "fudai", "fudai", "tozama", "fudai", "fudai",
"tozama", "fudai", "fudai", "fudai", "fudai", "fudai", "tozama",
"fudai", "fudai", "fudai", "fudai", "fudai", "fudai", "tozama",
"tozama", "fudai", "tozama", "tozama", "tozama", "tozama", "fudai",
"fudai", "tozama", "tozama"), distance = c(12.5366985071383,
272.697138147139, 40.4780423740381, 109.806349869662, 147.781805212839,
89.4280438527415, 49.1425850803745, 555.414271440522, 119.365138867582,
182.902536555383, 310.019126513348, 277.122207392514, 214.510428881317,
235.111617874157, 104.494518693549, 50.7561853895564, 343.308898045237,
151.796857505073, 36.0391449169937, 30.8214406651022, 343.294467363406,
135.841501028422, 154.798119311647, 317.739208576563, 3.33794280697559,
98.9182898110913, 422.915369767251, 194.957988642709, 87.6548263591412,
187.571370158631, 236.292608259126, 17.915709270268, 193.548578374405,
262.190146422316, 21.6219797945323, 121.199009527283, 261.670997612517,
202.2051991431, 125.418459536787, 275.964068539003, 190.112226847932,
20.1753302760961, 488.80323504215, 579.25515722891, 233.500797034697,
207.588349435329, 183.770003408524, 168.739293254246, 313.140075747773,
131.69228390613), age = c(1756, 1711, 1712, 1746, 1868, 1866,
1682, 1617, 1771, 1764, 1672, 1636, 1864, 1704, 1762, 1868, 1694,
1749, 1703, 1616, 1691, 1702, 1723, 1683, 1742, 1691, 1623, 1721,
1704, 1745, 1749, 1723, 1639, 1661, 1843, 1845, 1669, 1698, 1698,
1664, 1868, 1633, 1783, 1642, 1615, 1648, 1734, 1758, 1725, 1635
)), class = c("tbl_df", "tbl", "data.frame"), row.names = c(NA,
-50L))
还有一个基本模型
library("rpart")
sample_model <- rpart(formula = type ~ .,
data = sample_data,
method = "class",
control = rpart.control(xval = 50, minbucket = 5, cp = 0.05),
parms = list(split = "gini"))
rpart 文档说 sample_model$frame 中应该有一个名为“splits”的列，但它不在那里。引用:“拆分，每个节点的左右拆分标签的两列矩阵”https://www.rdocumentation.org/packages/rpart/versions/4.1-15/topics/rpart.object
sample_model$frame 或 sample_model 中的那些列在哪里？但是，我在
中看到了我想要的数据summary(sample_model)
这是怎么回事？
最佳答案
文档确实过时了。这是通过检查 summary.rpart 函数派生的提取器:
rpart_splits <- function(fit, digits = getOption("digits")) {
splits <- fit$splits
if (!is.null(splits)) {
ff <- fit$frame
is.leaf <- ff$var == "<leaf>"
n <- nrow(splits)
nn <- ff$ncompete + ff$nsurrogate + !is.leaf
ix <- cumsum(c(1L, nn))
ix_prim <- unlist(mapply(ix, ix + c(ff$ncompete, 0), FUN = seq, SIMPLIFY = F))
type <- rep.int("surrogate", n)
type[ix_prim[ix_prim <= n]] <- "primary"
type[ix[ix <= n]] <- "main"
left <- character(nrow(splits))
side <- splits[, 2L]
for (i in seq_along(left)) {
left[i] <- if (side[i] == -1L)
paste("<", format(signif(splits[i, 4L], digits)))
else if (side[i] == 1L)
paste(">=", format(signif(splits[i, 4L], digits)))
else {
catside <- fit$csplit[splits[i, 4L], 1:side[i]]
paste(c("L", "-", "R")[catside], collapse = "", sep = "")
}
}
cbind(data.frame(var = rownames(splits),
type = type,
node = rep(as.integer(row.names(ff)), times = nn),
ix = rep(seq_len(nrow(ff)), nn),
left = left),
as.data.frame(splits, row.names = F))
}
}
过滤 type == "main" 以仅获取主要拆分:
> fit <- rpart(Kyphosis ~ Age + Number + Start, data = kyphosis)
> rpart_splits(fit)
var type node ix left count ncat improve index adj
1 Start main 1 1 >= 8.5 81 1 6.76232996 8.5 0.0000000
2 Number primary 1 1 < 5.5 81 -1 2.86679493 5.5 0.0000000
3 Age primary 1 1 < 39.5 81 -1 2.25021152 39.5 0.0000000
4 Number surrogate 1 1 < 6.5 0 -1 0.80246914 6.5 0.1578947
5 Start main 2 2 >= 14.5 62 1 1.02052786 14.5 0.0000000
6 Age primary 2 2 < 55 62 -1 0.68486352 55.0 0.0000000
7 Number primary 2 2 < 4.5 62 -1 0.29753321 4.5 0.0000000
8 Number surrogate 2 2 < 3.5 0 -1 0.64516129 3.5 0.2413793
9 Age surrogate 2 2 < 16 0 -1 0.59677419 16.0 0.1379310
10 Age main 5 4 < 55 33 -1 1.24675325 55.0 0.0000000
11 Start primary 5 4 >= 12.5 33 1 0.28877005 12.5 0.0000000
12 Number primary 5 4 >= 3.5 33 1 0.17532468 3.5 0.0000000
13 Start surrogate 5 4 < 9.5 0 -1 0.75757576 9.5 0.3333333
14 Number surrogate 5 4 >= 5.5 0 1 0.69696970 5.5 0.1666667
15 Age main 11 6 >= 111 21 1 1.71428571 111.0 0.0000000
16 Start primary 11 6 >= 12.5 21 1 0.79365079 12.5 0.0000000
17 Number primary 11 6 >= 3.5 21 1 0.07142857 3.5 0.0000000
关于r - 从 R 中的 rpart 对象中提取拆分值，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/56209774/