日期未在rCharts多边形图中正确显示

Question

structure(list(Date = c("2013-11-17", "2013-11-18", "2013-11-19", 
"2013-11-20", "2013-11-21", "2013-11-22", "2013-11-23", "2013-11-25", 
"2013-11-26", "2013-11-27", "2013-11-28", "2013-11-29", "2013-11-30", 
"2013-12-02", "2013-12-03", "2013-12-04", "2013-12-05", "2013-12-06", 
"2013-12-07", "2013-12-09", "2013-12-10", "2013-12-11", "2013-12-12", 
"2013-12-13", "2013-12-14", "2013-12-16", "2013-12-17", "2013-11-17", 
"2013-11-18", "2013-11-19", "2013-11-20", "2013-11-21", "2013-11-22", 
"2013-11-23", "2013-11-25", "2013-11-26", "2013-11-27", "2013-11-28", 
"2013-11-29", "2013-11-30", "2013-12-01", "2013-12-02", "2013-12-03", 
"2013-12-04", "2013-12-05", "2013-12-06", "2013-12-07", "2013-12-09", 
"2013-12-10", "2013-12-11", "2013-12-12", "2013-12-13", "2013-12-14", 
"2013-12-16", "2013-12-17"), Catagory = structure(c(1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L), .Label = c("build", "client"), class = "factor"), 
    User_Name = c(1L, 4L, 6L, 6L, 5L, 7L, 5L, 5L, 3L, 5L, 2L, 
    4L, 5L, 2L, 3L, 2L, 2L, 5L, 5L, 7L, 3L, 4L, 3L, 4L, 3L, 2L, 
    2L, 1L, 5L, 6L, 6L, 6L, 7L, 5L, 5L, 3L, 5L, 2L, 4L, 5L, 1L, 
    6L, 4L, 5L, 4L, 6L, 5L, 12L, 4L, 4L, 3L, 5L, 5L, 3L, 3L), 
    type = c("obj1", "obj1", "obj1", "obj1", "obj1", "obj1", 
    "obj1", "obj1", "obj1", "obj1", "obj1", "obj1", "obj1", "obj1", 
    "obj1", "obj1", "obj1", "obj1", "obj1", "obj1", "obj1", "obj1", 
    "obj1", "obj1", "obj1", "obj1", "obj1", "obj2", "obj2", "obj2", 
    "obj2", "obj2", "obj2", "obj2", "obj2", "obj2", "obj2", "obj2", 
    "obj2", "obj2", "obj2", "obj2", "obj2", "obj2", "obj2", "obj2", 
    "obj2", "obj2", "obj2", "obj2", "obj2", "obj2", "obj2", "obj2", 
    "obj2")), .Names = c("Date", "Catagory", "User_Name", "type"
), row.names = c(NA, 55L), class = "data.frame") ->econ

library(rCharts)
attach(econ)
pic <- rPlot(User_Name~Date,color="type",data=econ,type="line")
pic$layer(x = "Date", y = "User_Name", data = econ, type = 'point', size = list(const = 2))
pic

以前的代码用于生成带有tooptip功能的rCharts。除了一个地方，生成的情节是可以的。如果将鼠标指针悬停在该行的某一点以检查该特定点的数据，您会注意到Date的值未正确显示。我该如何解决这个问题？