将年和月（“yyyy-mm”格式）转换为R？ [英] Converting year and month ("yyyy-mm" format) to a date in R?

问题描述

我有一个数据集，如下所示：

I have a dataset that looks like this:

Month    count
2009-01  12
2009-02  310
2009-03  2379
2009-04  234
2009-05  14
2009-08  1
2009-09  34
2009-10  2386

我想绘制数据（月份为x值并计为y值）。由于数据存在差距，我希望将本月的信息转换为日期。我试过：

I want to plot the data (months as x values and counts as y values). Since there are gaps in the data, I want to convert the Information for the Month into a date. I tried:

as.Date("2009-03", "%Y-%m")

但它没有工作。怎么了？看来，as.Date（）还需要一天，不能设置一天的标准值？哪个功能解决了我的问题？

But it did not work. Whats wrong? It seems that as.Date() requires also a day and is not able to set a standard value for the day? Which function solves my problem?

推荐答案

尝试这个。 （这里我们使用 text = Lines 来保持示例的自包含，但实际上我们将用文件名替换它。）

Try this. (Here we use text=Lines to keep the example self contained but in reality we would replace it with the file name.)

Lines <- "2009-01  12
2009-02  310
2009-03  2379
2009-04  234
2009-05  14
2009-08  1
2009-09  34
2009-10  2386"

library(zoo)
z <- read.zoo(text = Lines, FUN = as.yearmon)
plot(z)

X轴不是很漂亮的这个数据，但是如果你有更多的数据在现实中可能是可以的，或者您可以使用代码为一个花哨的X轴显示在示例部分？plot.zoo 。

The X axis is not so pretty with this data but if you have more data in reality it might be ok or you can use the code for a fancy X axis shown in the examples section of ?plot.zoo .

上面创建的动物园系列 z 有一个yearmon时间索引，如下所示：

The zoo series, z, that is created above has a "yearmon" time index and looks like this:

> z
Jan 2009 Feb 2009 Mar 2009 Apr 2009 May 2009 Aug 2009 Sep 2009 Oct 2009 
      12      310     2379      234       14        1       34     2386 

yearmon也可以单独使用：

> as.yearmon("2000-03")
[1] "Mar 2000"

注意

1. yearmon类对象以日历顺序排列。

1. "yearmon" class objects sort in calendar order.

这将以等间隔的间隔绘制每个点，这可能是想要的;然而，如果希望以与每个月的天数成比例的间隔间隔不等间隔绘制点，则将 z 的索引转换为Date class： time（z）< - as.Date（time（z））。

This will plot the monthly points at equally spaced intervals which is likely what is wanted; however, if it were desired to plot the points at unequally spaced intervals spaced in proportion to the number of days in each month then convert the index of z to "Date" class: time(z) <- as.Date(time(z)) .

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