qplot()中的行为可能不一致吗? [英] Possibly inconsistent behavior in qplot()?

问题描述

我正在尝试使用qplot()绘制一个简单的时间序列，就像使用plot()所做的那样. x变量为as.POSIXlt，而y只是一些连续测量.这是带有一些简短注释的代码.对于为什么这些data.frame行为不同的任何帮助，将不胜感激.正如您在下面看到的那样，我可以解决此问题，但是我很好奇为什么它不能按我预期的那样工作.

I'm trying to use qplot() to plot a simple time series as one might do using plot(). The x variable is as.POSIXlt and the y is just some continuous measurement. Here is the code with some brief comments. Any help on why these data.frames behave differently would be very much appreciated. As you can see below, I can work around the problem, but I'm curious as to why is doesn't work as I would expect.

一些细节:
平台:OS X 10.6.4
R版本:R 2.11.0

A few details:
platform: OS X 10.6.4
R version: R 2.11.0

免责声明:我意识到我可以深入研究源代码并自己解决这个问题.我从未使用过SO，因此认为这对本论坛来说可能是一个不错的话题.

Disclaimer: I realize that I could dig into the source code and figure this out myself. I've never used SO and thought that it might be a nice topic for this forum.

免责声明(2):我是ggplot2的新手

Disclaimer (2): I'm new to ggplot2

library(ggplot2)
ws.dat <- read.csv("~/path/to/filename.csv",header=F)
names(ws.dat) <- c("s","t","w")
ws.dat$new.t <- as.POSIXlt(ws.dat$t)
ws.dat[1:5,]
  ##       s                   t    w               new.t
  ## 1 29522 2005-07-02 00:00:00 5.00 2005-07-02 00:00:00
  ## 2 29522 2005-07-02 00:10:00 5.29 2005-07-02 00:10:00
  ## 3 29522 2005-07-02 00:20:00 5.48 2005-07-02 00:20:00
  ## 4 29522 2005-07-02 00:30:00 5.54 2005-07-02 00:30:00
  ## 5 29522 2005-07-02 00:40:00 5.49 2005-07-02 00:40:00


## the following works
plot(as.POSIXlt(ws.dat$t), ws.dat$w)

## doesn't work
qplot(as.POSIXlt(t), w, data = ws.dat)
  ## Error in if (length(range) == 1 || diff(range) == 0) { : 
  ## missing value where TRUE/FALSE needed

## doesn't work
ws.dat$new.t <- as.POSIXlt(ws.dat$t)
qplot(new.t, w, data = ws.dat)
  ## Same error as above

## Note - I could find a more elegant way of doing this; I'm just trying
##   to reproduce as fast as possible.
new.df <- data.frame(ws.dat$new.t, ws.dat$w)
new.df[1:5,]
  ##          ws.dat.new.t ws.dat.w
  ## 1 2005-07-02 00:00:00     5.00
  ## 2 2005-07-02 00:10:00     5.29
  ## 3 2005-07-02 00:20:00     5.48
  ## 4 2005-07-02 00:30:00     5.54
  ## 5 2005-07-02 00:40:00     5.49

## 'works as *I* would expect'; this is != 'works *as* expected' 
qplot(ws.dat.new.t, ws.dat.w, data = new.df)

推荐答案

使用POSIXct-POSIXlt不适合包含在数据帧中.当您使用data.frame创建变量时，它会自动强制为POSIXct.

Use POSIXct - POSIXlt is not suitable for inclusion into data frames. When you use data.frame to create the variable it is automatically coerced to POSIXct.

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