r - 使用 emphasis.strong.cells 强调单元格失败 - POSIXct 相关？

Question

我正在尝试显示下表(其中包含类 POSIXct 的两列)并强调包含特定值 ( "B" ) 的单元格。

> test
   bikeid start_station           starttime end_station             endtime
1       1             A 2017-09-25 01:00:00           B 2017-09-25 01:30:00
2       1             B 2017-09-25 07:30:00           C 2017-09-25 08:00:00
3       1             C 2017-09-25 10:00:00           A 2017-09-25 10:30:00
4       1             A 2017-09-25 13:00:00           C 2017-09-25 13:30:00
5       1             C 2017-09-25 15:30:00           B 2017-09-25 16:00:00
6       1             B 2017-09-25 18:00:00           B 2017-09-25 18:30:00
7       1             B 2017-09-25 19:00:00           A 2017-09-25 19:30:00
8       1             А 2017-09-25 20:00:00           C 2017-09-25 20:30:00
9       1             C 2017-09-25 22:00:00           B 2017-09-25 22:30:00
10      1             B 2017-09-25 23:00:00           C 2017-09-25 23:30:00

当我使用下面的代码时，表格显示成功:

library(pander)
panderOptions('table.split.table', Inf)
pander(test)

但是，当我包含 emphasize.strong.cells 时指定要强调的单元格，表格失败，我收到错误消息:

panderOptions('table.split.table', Inf)
emphasize.strong.cells(which(test == "B"))
pander(test)

# Error in as.POSIXlt.character(x, tz, ...) : 
#  character string is not in a standard unambiguous format
#  Calls: <Anonymous> ... as.POSIXct.default -> as.POSIXct -> as.POSIXlt -> 
# as.POSIXlt.character
# Execution halted

即使列包含 POSIXct值被完全删除，代码仍然失败。

为什么会发生这种情况，正确的解决方法是什么？

这是数据集的示例:

> dput(test)
structure(list(bikeid = c(1, 1, 1, 1, 1, 1, 1, 1, 1, 1), start_station = c("A", 
"B", "C", "A", "C", "B", "B", "А", "C", "B"), starttime = structure(c(1506315600, 
1506339000, 1506348000, 1506358800, 1506367800, 1506376800, 1506380400, 
1506384000, 1506391200, 1506394800), class = c("POSIXct", "POSIXt"
), tzone = ""), end_station = c("B", "C", "A", "C", "B", "B", 
"A", "C", "B", "C"), endtime = structure(c(1506317400, 1506340800, 
1506349800, 1506360600, 1506369600, 1506378600, 1506382200, 1506385800, 
1506393000, 1506396600), class = c("POSIXct", "POSIXt"), tzone = "")), .Names = c("bikeid", 
"start_station", "starttime", "end_station", "endtime"), row.names = c(NA, 
-10L), class = "data.frame")

Answer 1

您的问题与emphasize.strong.cells无关, 但是由您在 which 中进行的比较引起的: test == "B" .您正在比较 character “B”与整个数据集“测试”。在“测试”中，您的焦点变量是 character s，但你也有一些非 character变量，即两个 POSIXct变量。因此，您正在对不同类型的参数进行比较 ( == )。然后看?Comparison :

If the two arguments are atomic vectors of different types, one is coerced to the type of the other.

当您尝试将“B”与 POSIXct 进行比较时变量，R 试图将“B”强制为 POSIXct失败了:

as.POSIXct("2017-09-25 01:00:00") == "B"
# Error in as.POSIXlt.character(x, tz, ...) : 
#   character string is not in a standard unambiguous format

只是为了展示何时强制 RHS character 的示例会有效:

as.POSIXct("2017-09-25 01:00:00") == "2017-09-25 01:00:00"
# [1] TRUE 

如果你有一个 Date 也会发生类似的问题数据框中的变量:

as.Date("2017-09-25") == "B"
# Error in charToDate(x) : 
#   character string is not in a standard unambiguous format

因此，正如我在评论中提到的，针对您的情况，一种解决方法是强制 POSIXct列到 character在进行比较之前。

---

另一方面，如果您一直在寻找要强调的某个数字值(例如 test > 10 )，则与 Date 进行比较或 POSIXct列不会导致错误(检查例如 typeof(as.POSIXct("2017-09-25 01:00:00")) )。

---

一个小例子:

d <- data.frame(time = as.POSIXct("2017-09-25 21:30:20") + 0:1,
                x = c("A", "B"), y = 1:2)
d

emphasize.strong.cells(which(d == "B", arr.ind = TRUE))
# Error in as.POSIXlt.character(x, tz, ...) : 
#   character string is not in a standard unambiguous format

d$time <- as.character(d$time)
emphasize.strong.cells(which(d == "B", arr.ind = TRUE))
pander(d)
# ---------------------------------
#          time             x     y 
# --------------------- ------- ---
#   2017-09-25 21:30:20     A     1 
# 
#   2017-09-25 21:30:21   **B**   2 
# ---------------------------------


emphasize.strong.cells(which(d == 1, arr.ind = TRUE))
pander(d)
# ---------------------------------
#         time           x     y   
# --------------------- --- -------
#  2017-09-25 21:30:20   A   **1** 
#  
#  2017-09-25 21:30:21   B     2   
# ---------------------------------