将值分配给名称中带有"点"的变量

Question

我是R的新手,正在尝试以下代码.令我惊讶的是,分配的内容ret$log.id实际上也会导致分配给相同的值ret$log.例如,

 ret <- c()
 ret$log.id <- 'a'

运行以下将返回 "a"

ret$log

这是R应该做的吗？我希望有人可以给我一些洞察力.

谢谢,

Answer 1

是的,$运营商正在做一些部分匹配.您可以使用以下内容稍微探索一下此行为:

ret <- c()
ret$log.id <- "a"

ret$l #Returns "a"

ret$log.at <- "b"

现在看看返回的内容如下:

ret$l
ret$log
ret$log.i
ret$log.a

Answer 2

详细说明部分匹配的boner.从帮助页面$:

根据论据:

name     A literal character string or a name (possibly backtick quoted).
For extraction, this is normally (see under ‘Environments’) partially matched to the names 
of the object.

然后在字符索引下:

Character indices can in some circumstances be partially matched (see pmatch) to the 
names or dimnames of the object being subsetted (but never for subassignment). 

也在字符索引下:

Thus the default behaviour is to use partial matching only when extracting from 
recursive objects (except environments) by $. Even in that case, warnings can be 
switched on by options(warnPartialMatchAttr = TRUE).

有更多细节参考names,pmatch但我已经清除了它.