我有几块使用管道的代码，当我重新加载以前从未发生过的rStudio时，其中许多已经停止工作。之前的代码如下：
library(dplyr)
df <- data.frame(a = c("A", "B", "A","B" ,"A" ,"B"), b = c(1, 2, 3,4,5,6))
df %>% count(a)
但是现在它告诉我Error in UseMethod("as.quoted") : no applicable method for 'as.quoted' applied to an object of class "function"必须写为：
count(df$a)
或：
df %>% count(vars="a")
关于我可以做什么的任何想法？ rStudio说它是最新的，我正在使用R 3.6.1，并且我还尝试了重新安装dplyr。
编辑： 这是来自sessionInfo（）的信息
R version 3.6.1 (2019-07-05)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 18363)
Matrix products: default
locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] shiny_1.4.0 lubridate_1.7.4 tidyr_1.0.0 plyr_1.8.4
[5] dplyr_0.8.3
loaded via a namespace (and not attached):
[1] Rcpp_1.0.3 rstudioapi_0.10 knitr_1.26 magrittr_1.5
[5] tidyselect_0.2.5 xtable_1.8-4 R6_2.4.1 rlang_0.4.2
[9] fastmap_1.0.1 stringr_1.4.0 tools_3.6.1 xfun_0.11
[13] htmltools_0.4.0 assertthat_0.2.1 digest_0.6.23 tibble_2.1.3
[17] lifecycle_0.1.0 crayon_1.3.4 later_1.0.0 purrr_0.3.3
[21] promises_1.1.0 vctrs_0.2.0 rsconnect_0.8.15 zeallot_0.1.0
[25] mime_0.7 glue_1.3.1 stringi_1.4.3 compiler_3.6.1
[29] pillar_1.4.2 backports_1.1.5 httpuv_1.5.2 pkgconfig_2.0.3