使用reduce和left_join来合并table_basetable_atable_b。方法A可以工作，但必须输入对象名称，有点无聊。方法B可以得到对象名称，但不能返回正确的结果，如何修复？谢谢！

library(tidyverse)
table_base <- data.frame(cat=c("a","b","c","d"))

table_a <- data.frame(cat=c("a","b"),
                      value=c(1,2))

table_b <- data.frame(cat=c("a","c","d"),
                      value=c(7,9,10))

# method A: ok, but have to input object name one by one in list

reduce(list(table_base,table_a,table_b),left_join,by='cat') 


# method B: can't work
reduce(list(mget(ls(pattern="^table"))),left_join,by='cat')

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