gamlasso中使用offset项触发下标错误的技术求助

问题复现 #

使用gamlasso生成变量平滑估计功能正常，但加入offset项后报错，复现代码如下：

构建线性项模型矩阵 #

# 线性项的模型矩阵
gamlasso_data$X <- model.matrix(~ as.factor(time) + age_0,
                                data = gamlasso_data)[,-1]   # -1 移除默认截距列

gamlasso模型代码（注释offset时正常运行） #

# 公式法 - 年龄/时间模型
gamlassofit = gamlasso(count ~ X +
        #                      population_est + 
                               s(age, time, bs='fs'),
                       family = 'poisson',
                       data = gamlasso_data,
                       num.knots = -1,
                       seed = 1,
        #              offset = log(gamlasso_data$population_est),
                       num.iter = 10) 

取消注释offset参数后触发错误：

Must extract column with a single valid subscript.
x Subscript var has the wrong type double.
i It must be numeric or character.

对比：普通GAM模型添加offset正常运行 #

fitted_gam <- gam(count ~ s(age, time, bs='fs'),
                  data = gamlasso_data,
                  family = poisson,
                  offset = log(population_est),
                  method = "REML")

解决方法 #

根据错误提示，gamlasso的offset参数对输入格式的要求和gam不同，可尝试以下两种方案：

1. 将offset写入模型公式
   把offset项直接整合到模型公式中，删除单独的offset参数：

   gamlassofit = gamlasso(count ~ X + s(age, time, bs='fs') + offset(log(population_est)),
                          family = 'poisson',
                          data = gamlasso_data,
                          num.knots = -1,
                          seed = 1,
                          num.iter = 10)
   

2. 提前生成offset列并传入列名
   先将计算后的offset值作为新列加入数据集，再给offset参数传入列名（字符或数值型下标）：

   # 提前计算offset列
   gamlasso_data$log_pop <- log(gamlasso_data$population_est)
   
   # 调用gamlasso时传入列名
   gamlassofit = gamlasso(count ~ X + s(age, time, bs='fs'),
                          family = 'poisson',
                          data = gamlasso_data,
                          num.knots = -1,
                          seed = 1,
                          offset = "log_pop", # 或用列的数值下标，比如如果是第5列就写5
                          num.iter = 10)
   

内容的提问来源于stack exchange，提问作者Olivander