变量名字不能有%号吧。

The set of symbols which can be used in R names depends on the operating system and country
within which R is being run (technically on the locale in use). Normally all alphanumeric
symbols are allowed1 (and in some countries this includes accented letters) plus ‘.’ and ‘_’, with
the restriction that a name must start with ‘.’ or a letter, and if it starts with ‘.’ the second
character must not be a digit. Names are currently effectively unlimited, but were limited to
256 bytes prior to R 2.13.0. （from R-intro）
不知道为什么楼主会发现有变量名是%WC的。

LZ好奇怪的要求啊，为什么不能改名字呢？

去掉%，换个其它前缀

还是改名吧，建议楼主不要把变量的第一个字符用符号表示