WriteXLS pacakage（R）中的“envir = parent.frame（））”中的错误：意外'）'

Question

数据框如下所示：

str(espr2)
#'data.frame':  5856 obs. of  2 variables:
# $ date: POSIXct, format: "2015-04-01 09:07:42" "2015-04-01 09:08:01" "2015-04-01 09:15:03" ...
# $ es  : num  31 29.5 18.5 8.8 9.6 ...

使用以下代码创建Excel文件时：

library(WriteXLS)
testPerl(perl = "perl", verbose = TRUE)
WriteXLS(espr2, ExcelFileName = "espr2.xls", SheetNames = NULL, perl = "perl", 
verbose = FALSE, Encoding = c("UTF-8", "latin1", "cp1252"),        
row.names = FALSE, col.names = TRUE, AdjWidth = FALSE, AutoFilter = FALSE, 
BoldHeaderRow = FALSE, FreezeRow = 0, FreezeCol = 0, envir = parent.frame())

R控制台显示错误

envir = parent.frame())
Error: unexpected ')' in "envir = parent.frame())"