我有一种以不守规矩的时间格式导出数据的工具。我需要将date和time向量组合成以下datetime格式的新POSIXct向量：%Y-%m-%d %H:%M:%S。出于好奇，我尝试使用as.POSIXct()，strftime()和strptime()以三种不同的方式执行此操作。在下面使用我的示例数据时，只有as.POSIXct()和strftime()函数有效，但我很好奇为什么strptime()正在生成NAs？另外，我无法使用strftime()将POSIXct输出转换为as.POSIXct()对象...
在我的真实数据上尝试这些相同的功能时（其中我只提供了第一行的行），我遇到了一个完全不同的问题。只有strftime()功能正在运行。出于某种原因，as.POSIXct()函数也生成NAs，这是我将datetime转换为POSIXct对象时实际需要的唯一命令...
似乎这些功能之间存在细微差别，我想知道如何更有效地使用它们。谢谢！
可重复示例：
## Creating dataframe:
date <- c("2017-04-14", "2017-04-14","2017-04-14","2017-04-14")
time <- c("14:24:24.992000","14:24:25.491000","14:24:26.005000","14:24:26.511000")
value <- c("4.106e-06","4.106e-06","4.106e-06","4.106e-06")
data <- data.frame(date, time)
data <- data.frame(data, value) ## I'm sure there is a better way to combine three vectors...
head(data)
## Creating 3 different datetime vectors:
## This works in my example code, but not with my real data...
data$datetime1 <- as.POSIXct(paste(data$date, data$time), format = "%Y-%m-%d %H:%M:%S",tz="UTC")
class(data$datetime1)
## This is producing NAs, and I'm not sure why:
data$datetime2 <- strptime(paste(data$date, data$time), format = "%Y-%m-%d %H:%M%:%S", tz = "UTC")
class(data$datetime2)
## This is working just fine
data$datetime3 <- strftime(paste(data$date, data$time), format = "%Y-%m-%d %H:%M%:%S", tz = "UTC")
class(data$datetime3)
head(data)
## Since I cannot get the as.POSIXct() function to work with my real data, I tried this workaround. Unfortunately I am running into trouble...
data$datetime4 <- as.POSIXct(x$datetime3, format = "%Y-%m-%d %H:%M%:%S", tz = "UTC")
链接到真实数据： here
使用 real_data.txt的示例：
## Reading in the file:
fpath <- "~/real_data.txt"
x <- read.csv(fpath, skip = 1, header = FALSE, sep = "", stringsAsFactors = FALSE)
names(x) <- c("date","time","bscat","scat_coef","pressure_mbar","temp_K","CH1","CH2") ## This is data from a Radiance Research Integrating Nephelometer Model M903 for anyone who is interested!
## If anyone could get this to work that would be awesome!
x$datetime1 <- as.POSIXct(paste(x$date, x$time), format = "%Y-%m-%d %H:%M%:%S", tz = "UTC")
## This still doesn't work...
x$datetime2 <- strptime(paste(x$date, x$time), format = "%Y-%m-%d %H:%M%:%S", tz = "UTC")
## This works:
x$datetime3 <- strftime(paste(x$date, x$time), format = "%Y-%m-%d %H:%M%:%S", tz = "UTC")
## But I cannot convert from strftime character to POSIXct object, so it doesn't help me at all...
x$datetime4 <- as.POSIXct(x$datetime3, format = "%Y-%m-%d %H:%M%:%S", tz = "UTC")
head(x)
解决方案：
我没有为as.POSIXct()函数提供正确的格式字符串。将%Y-%m-%d %H:%M%:%S更改为%Y-%m-%d %H:%M:%S后，data$datetime2，data$datetime4，x$datetime1和x$datetime2工作正常！非常感谢PhilC进行调试！
答案 0 :(得分：3)
对于您的真实数据问题，请将%m%替换为%m：
## Reading in the file:
fpath <- "c:/r/data/real_data.txt"
x <- read.csv(fpath, skip = 1, header = FALSE, sep = "", stringsAsFactors = FALSE)
names(x) <- c("date","time","bscat","scat_coef","pressure_mbar","temp_K","CH1","CH2") ## This is data from a Radiance Research Integrating Nephelometer Model M903 for anyone who is interested!
## issue was the %m% - fixed
x$datetime1 <- as.POSIXct(paste(x$date, x$time), format = "%Y-%m-%d %H:%M:%S", tz = "UTC")
## Here too - fixed
x$datetime2 <- strptime(paste(x$date, x$time), format = "%Y-%m-%d %H:%M:%S", tz = "UTC")
head(x)
答案 1 :(得分：1)
导致NA的格式字符串错误;试试这个：
## This is no longer producing NAs:
data$datetime2 <- strptime(paste(data$date, data$time), format = "%Y-%m-%d %H:%M:%S",tz="UTC")
class(data$datetime2)
答案 2 :(得分：0)
格式化为“％Y-％m-％d％H：％M：％OS”是通用视图。要将小数秒设置为特定的小数位数，请调用degits.sec的选项，例如：
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<style type="text/css">
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</marker>
<svg id="Box">
<rect width="100" height="85" x="1" y="1" />
<text x="5" y="20">The box</text>
<svg x="10" y="25">
<rect width="70" height="50" x="1" y="1" />
<text x="5" y="20">Box</text>
<text x="5" y="40">Contents</text>
</svg>
</svg>
</defs>
<svg>
<svg x="10" y="120">
<rect width="100" height="50" x="1" y="1" />
<text x="5" y="20">Data</text>
<text x="5" y="40">source</text>
</svg>
<svg x="150">
<use href="#Box" y="1" />
<use href="#Box" y="100" />
<use href="#Box" y="200" />
</svg>
<svg x="300" y="120">
<rect width="100" height="50" x="1" y="1" />
<text x="5" y="20">Database</text>
<text x="5" y="40">server</text>
</svg>
<line x1="100" y1="120" x2="148" y2="40" style="marker-end:url(#EndArrow)" />
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