R：使用预测函数为预测添加标准误差和置信区间

我制作了这个模型：

model <- lm(mpg ~ wt, mtcars)

我可以用expand.grid做同样的预测，如下所示：

expand_grid_df <- expand.grid(wt  = 1:5)
expand_grid_df$fit <- predict(model, expand_grid_df)
expand_grid_df

  wt      fit
1  1 31.94065
2  2 26.59618
3  3 21.25171
4  4 15.90724
5  5 10.56277

如何为标准误差和拟合的上/下置信区间添加列以扩展网格df，就像实际的df一样？

这样做：

expand_grid_df <- expand.grid(wt  = 1:5)
expand_grid_df$fit <- predict(model, expand_grid_df, se.fit=TRUE, interval="confidence")$fit
expand_grid_df$se.fit <- predict(model, expand_grid_df, se.fit=TRUE)$se.fit
expand_grid_df

  wt  fit.fit  fit.lwr  fit.upr    se.fit
1  1 31.94065 29.18042 34.70089 1.3515519
2  2 26.59618 24.82389 28.36848 0.8678067
3  3 21.25171 20.12444 22.37899 0.5519713
4  4 15.90724 14.49018 17.32429 0.6938618
5  5 10.56277  8.24913 12.87641 1.1328743

expand_grid_df <- expand.grid(wt  = 1:5)
expand_grid_df$fit <- predict(model, expand_grid_df, se.fit=TRUE, interval="confidence")$fit
expand_grid_df$se.fit <- predict(model, expand_grid_df, se.fit=TRUE)$se.fit
expand_grid_df

  wt  fit.fit  fit.lwr  fit.upr    se.fit
1  1 31.94065 29.18042 34.70089 1.3515519
2  2 26.59618 24.82389 28.36848 0.8678067
3  3 21.25171 20.12444 22.37899 0.5519713
4  4 15.90724 14.49018 17.32429 0.6938618
5  5 10.56277  8.24913 12.87641 1.1328743