[英]How to change x-axis label intervals for a datetime series in R
我创建了一个在x轴上具有时间序列并在y轴上计数值的图表。 我想知道如何更改时间序列x轴上的间隔,以使时间间隔为每3小时一次。 我不确定如何将类似at = seq(0,100,10)的简单方法应用于时间序列。 其次,是否可以对数据集中未使用的时间使用文本标签? 即下面的示例数据以10分钟为间隔,从09:29开始,但是是否有可能使用x轴上的小时值呢? 我假设这样做的唯一方法是手动在文本字符串中列出时间,但想知道我是否丢失了什么? 任何建议将不胜感激。
示例数据:
> dput(df)
structure(list(datetime = structure(c(1396603740, 1396604340,
1396604940, 1396605540, 1396606140, 1396606740, 1396607340, 1396607940,
1396608540, 1396609140, 1396609740, 1396610340, 1396610940, 1396611540,
1396612140, 1396612740, 1396613340, 1396613940, 1396614540, 1396615140,
1396615740, 1396616340, 1396616940, 1396617540, 1396618140, 1396618740,
1396619340, 1396619940, 1396620540, 1396621140, 1396621740, 1396622340,
1396622940, 1396623540, 1396624140, 1396624740, 1396625340, 1396625940,
1396626540, 1396627140, 1396627740, 1396628340, 1396628940, 1396629540,
1396630140, 1396630740, 1396631340, 1396631940, 1396632540, 1396633140,
1396633740, 1396634340, 1396634940, 1396635540, 1396636140, 1396636740,
1396637340, 1396637940, 1396638540, 1396639140, 1396639740, 1396640340,
1396640940, 1396641540, 1396642140, 1396642740, 1396643340, 1396643940,
1396644540, 1396645140, 1396645740, 1396646340, 1396646940, 1396647540
), class = c("POSIXct", "POSIXt"), tzone = "UTC"), count = c(46,
45, 47, 43, 49, 46, 46, 44, 44, 44, 45, 49, 50, 46, 45, 43, 47,
48, 48, 46, 47, 46, 46, 44, 46, 44, 45, 49, 44, 46, 44, 48, 44,
42, 44, 50, 44, 44, 48, 43, 43, 46, 44, 49, 49, 44, 42, 45, 45,
48, 46, 45, 46, 43, 40, 50, 39, 42, 48, 44, 44, 46, 43, 47, 46,
41, 43, 43, 46, 48, 45, 48, 43, 42)), .Names = c("datetime",
"count"), row.names = c(NA, -74L), class = "data.frame")
>head(df)
datetime count
1 2014-04-04 09:29:00 46
2 2014-04-04 09:39:00 45
3 2014-04-04 09:49:00 47
4 2014-04-04 09:59:00 43
5 2014-04-04 10:09:00 49
6 2014-04-04 10:19:00 46
示例代码(用于绘制所有日期时间):
#Convert datetime character string to POSIXct format
df$datetime = as.POSIXct(strptime(df$datetime, format="%d/%m/%Y %H:%M:%S"), tz="UTC")
plot(df$datetime, df$count, axes=FALSE)
axis(2,las=2)
axis.POSIXct(1, at=df$datetime, labels=format(df$datetime, “%H:%M")) #datetime format can be changed as desired
lines(df$datetime, df$count, col="grey22")
首先,让我们更正axis.POSIXct
调用:
axis.POSIXct(1, at=df$datetime, format="%H:%M")
通过参数format
您可以定义时间格式,而不必一一格式化每个标签。 at
参数是我们将用来定义刻度线的位置的参数。
首先,您可以使用应用于POSIXt对象的seq
定义日期序列(请参阅?seq.POSIXt
),在其中可以为自变量by
提供自定义名称,例如"3 hours"
:
一个字符串,包含“秒”,“分钟”,“小时”,“天”,“ DSTday”,“星期”,“月”或“年”之一。 可以选择在其前跟一个(正数或负数)整数和一个空格,或后跟“ s”。
因此:
seq(df$datetime[1], tail(seq$datetime,1), by="3 hours")
# [1] "2014-04-04 09:29:00 UTC" "2014-04-04 12:29:00 UTC" "2014-04-04 15:29:00 UTC" "2014-04-04 18:29:00 UTC" "2014-04-04 21:29:00 UTC"
现在,要使序列从一个小时开始,就需要使用round
(请参见?round.POSIXt
):
round(df$datetime[1], "hour")
# [1] "2014-04-04 09:00:00 UTC"
seq(round(df$datetime[1],"hour"), tail(df$datetime,1), by="3 hours")
# [1] "2014-04-04 09:00:00 UTC" "2014-04-04 12:00:00 UTC" "2014-04-04 15:00:00 UTC" "2014-04-04 18:00:00 UTC" "2014-04-04 21:00:00 UTC"
总而言之,您的代码变为:
df <- structure(list(datetime = structure(c(1396603740, 1396604340, 1396604940, 1396605540, 1396606140, 1396606740, 1396607340, 1396607940, 1396608540, 1396609140, 1396609740, 1396610340, 1396610940, 1396611540, 1396612140, 1396612740, 1396613340, 1396613940, 1396614540, 1396615140, 1396615740, 1396616340, 1396616940, 1396617540, 1396618140, 1396618740, 1396619340, 1396619940, 1396620540, 1396621140, 1396621740, 1396622340, 1396622940, 1396623540, 1396624140, 1396624740, 1396625340, 1396625940, 1396626540, 1396627140, 1396627740, 1396628340, 1396628940, 1396629540, 1396630140, 1396630740, 1396631340, 1396631940, 1396632540, 1396633140, 1396633740, 1396634340, 1396634940, 1396635540, 1396636140, 1396636740, 1396637340, 1396637940, 1396638540, 1396639140, 1396639740, 1396640340, 1396640940, 1396641540, 1396642140, 1396642740, 1396643340, 1396643940, 1396644540, 1396645140, 1396645740, 1396646340, 1396646940, 1396647540), class = c("POSIXct", "POSIXt"), tzone = "UTC"), count = c(46, 45, 47, 43, 49, 46, 46, 44, 44, 44, 45, 49, 50, 46, 45, 43, 47, 48, 48, 46, 47, 46, 46, 44, 46, 44, 45, 49, 44, 46, 44, 48, 44, 42, 44, 50, 44, 44, 48, 43, 43, 46, 44, 49, 49, 44, 42, 45, 45, 48, 46, 45, 46, 43, 40, 50, 39, 42, 48, 44, 44, 46, 43, 47, 46, 41, 43, 43, 46, 48, 45, 48, 43, 42)), .Names = c("datetime", "count"), row.names = c(NA, -74L), class = "data.frame")
plot(df$datetime, df$count, axes=FALSE)
axis(2,las=2)
axis.POSIXct(1, at=seq(from=round(df$datetime[1],"hour"),
to=tail(df$datetime,1),
by="3 hours"),
format="%H:%M")
lines(df$datetime, df$count, col="grey22")
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