R：xtable和日期

问题描述

我有以下数据：

transaction <- c(1,2,3);
date <- c("2010-01-31","2010-02-28","2010-03-31");
type <- c("debit", "debit", "credit");
amount <- c(-500, -1000.97, 12500.81);
oldbalance <- c(5000, 4500, 17000.81)
evolution <- data.frame(transaction, date, type, amount, oldbalance, row.names=transaction, stringsAsFactors=FALSE);
evolution <- transform(evolution, newbalance = oldbalance + amount);
evolution

运行

> library(xtable)
> xtable(evolution)

工作正常。但是如果我添加了

works fine. But if I add the line

evolution$date <- as.Date(evolution$date, "%Y-%m-%d");

给予

transaction <- c(1,2,3);
date <- c("2010-01-31","2010-02-28","2010-03-31");
type <- c("debit", "debit", "credit");
amount <- c(-500, -1000.97, 12500.81);
oldbalance <- c(5000, 4500, 17000.81)
evolution <- data.frame(transaction, date, type, amount, oldbalance, row.names=transaction, stringsAsFactors=FALSE);
evolution$date <- as.Date(evolution$date, "%Y-%m-%d");
evolution <- transform(evolution, newbalance = oldbalance + amount);
evolution

然后运行 xtable 给出

但使用 xtable 在这种情况下做一些过滤日期

But it can be useful to use xtable in such a case to do some filtering of dates

evolution$date <- as.Date(evolution$date, "%Y-%m-%d")
startdate <-as.Date("2010-02-01");
enddate <-as.Date("2010-03-30");
newdate <-evolution[which (evolution$date >= startdate & evolution$date <= enddate),]
newdate


> newdate
  transaction       date  type   amount oldbalance newbalance
2           2 2010-02-28 debit -1000.97       4500    3499.03
> xtable(newdate)
Error in Math.Date(x + ifelse(x == 0, 1, 0)) :
  abs not defined for Date objects

推荐答案

这可以说是 xtable 中的错误可能要向维护者报告。

This is arguably a bug in xtable - you may want to report it to the maintainer.

临时解决方法是调用 as.character（）在 xtable 的解释中，除了Date之外，我可以想到POSIXt，但可能还有其他的），例如：

A temporary work-around is to call as.character() on the classes that xtable misinterprets (apart from "Date" I can think of "POSIXt" but there may be others), e.g.:

xtable <- function(x, ...) {
   for (i in which(sapply(x, function(y) !all(is.na(match(c("POSIXt","Date"),class(y))))))) x[[i]] <- as.character(x[[i]])
   xtable::xtable(x, ...)
}

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