R包中有偏移项的分段 [英] R Package segmented with an offset term

问题描述

我在R中使用包 segmented .我首先使用glm函数将Poisson glm与对数链接函数配合使用，该函数包括偏移项，例如:

I am using package segmented in R. I first fitted a Poisson glm with a log link function using the glm function that includes an offset term like:

M1=glm(Y~X1+X2+X3+offset(log(X)),data=dat.1,family=poisson)

M1正确安装.接下来，我尝试通过使用R中分段的包来拟合分段的glm:

M1 is fitted without any error. Next I tried to fit a segmented glm by using the package segmented in R as:

library(segmented)
seg.1=segmented(M1,seg.Z=~X1,psi=list(X1=c(0.5)))

我遇到以下错误:

Error in offset(log(X)) : object 'X' not found

我的错误在哪里?非常感谢.

Where is my mistake here? Thanks a lot.

推荐答案

在调用glm时明确提供X(例如sample_dat$X)的位置即可达到目的.

Explicitly providing the location of X (e.g. sample_dat$X) in the call to glm does the trick.

以下是可重现的示例:

library(segmented)

# sample data
set.seed(101)
sample_dat <- data.frame(Y = rpois(100, 3), X1 = rnorm(100), X2 = rnorm(100), X = rpois(100, 100))

# fit model 
M1 = glm(Y ~ X1 + X2, data = sample_dat, offset = log(sample_dat$X), family = poisson)
seg.1 = segmented(M1, seg.Z=~X1, psi=list(X1 = c(0.5)), data = sample_dat)

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