问题
Installed R 2.15.2 on a new machine and ggplot2. The grid package is no longer supported in this latest version of R, but ggplot2 uses grid for the arrow() function, as in these examples.
http://docs.ggplot2.org/current/geom_segment.html
Haven't been able to find a workaround. Any suggestions?
回答1:
Maybe you think that grid is no more supported because of the message displayed on its CRAN page ? But if it is written that Package ‘grid’ was removed from the CRAN repository, it is because it is now part of the base R distribution, as mentioned on Paul Murrell's grid page.
So library(grid) and the arrow function should work fine.
Some of the confusion may be due to the fact that grid was loaded automatically by previous versions of ggplot (making grid functions visible/accessible to the user); now it's referred to via NAMESPACE imports instead, so you need to explicitly load grid if you want to use grid functions (or look at their help pages).
来源：https://stackoverflow.com/questions/14677035/arrow-in-ggplot2-no-longer-supported