从土质模型中提取边坡
从土质模型中提取边坡
提问于 2017-04-12 15:58:16
我有一些使用earth模型的数据。我对不同线条的斜率感兴趣，但是看看模型摘要，我没有得到我的预期值。
library(earth)
library(dplyr)
library(ggplot2)
d = structure(list(x = c(9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30), y = c(0.151534750704409,
0.0348452707597105, -0.0913494247372798, -0.214465577974757,
-0.365251164825619, -0.528214103496014, -0.614970081844732,
-0.922572314358796,
-1.15911158401926, -1.36432638285029, -1.51587576144429, -1.63708705686248,
-1.7530889072188, -1.86142968143915, -1.98159646754281, -2.0994478459505,
-2.23037530743309, -2.3421669680425, -2.40621060828366, -2.55432043723978,
-2.73246980567199, -2.92496136528975)), .Names = c("x", "y"), row.names =
c(NA, -22L), class = c("tbl_df", "tbl", "data.frame"))
mod = earth(y ~ x, data = d)
d$pred = predict(mod, newdata = d)
summary(mod, style = 'pmax')以下是我的总结：
Call: earth(formula=y~x, data=d)
y =
-1.314958
- 0.06811314 * pmax(0, x - 16)
+ 0.1518165 * pmax(0, 19 - x)
- 0.05124021 * pmax(0, x - 19)
Selected 4 of 4 terms, and 1 of 1 predictors
Termination condition: RSq changed by less than 0.001 at 4 terms
Importance: x
Number of terms at each degree of interaction: 1 3 (additive model)
GCV 0.004496406 RSS 0.04598597 GRSq 0.9953947 RSq 0.9976504然而，当我看我的模型时，三个不同的斜率看起来都是负面的：
ggplot(d, aes(x, y)) +
geom_point() +
geom_line(aes(x, pred)) +
theme(aspect.ratio = 1)
我如何得到这三个负斜率的数值？
回答 1
Stack Overflow用户
回答已采纳
发布于 2017-04-12 16:21:13
mod$coefficients给出了系数。如果系数在-x上，te斜率将是系数的负值。你可以做mod$coefficients %>% {ifelse(grepl('-x', rownames(.)) , -., .)}来得到斜坡(或者只是在思想上颠倒了-x的部分)。
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原文链接：
https://stackoverflow.com/questions/43374384
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