[英]How to change x-axis label intervals for a datetime series in R
我創建了一個在x軸上具有時間序列並在y軸上計數值的圖表。 我想知道如何更改時間序列x軸上的間隔,以使時間間隔為每3小時一次。 我不確定如何將類似at = seq(0,100,10)的簡單方法應用於時間序列。 其次,是否可以對數據集中未使用的時間使用文本標簽? 即下面的示例數據以10分鍾為間隔,從09:29開始,但是是否有可能使用x軸上的小時值呢? 我假設這樣做的唯一方法是手動在文本字符串中列出時間,但想知道我是否丟失了什么? 任何建議將不勝感激。
示例數據:
> 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
示例代碼(用於繪制所有日期時間):
#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,讓我們更正axis.POSIXct
調用:
axis.POSIXct(1, at=df$datetime, format="%H:%M")
通過參數format
您可以定義時間格式,而不必一一格式化每個標簽。 at
參數是我們將用來定義刻度線的位置的參數。
首先,您可以使用應用於POSIXt對象的seq
定義日期序列(請參閱?seq.POSIXt
),在其中可以為自變量by
提供自定義名稱,例如"3 hours"
:
一個字符串,包含“秒”,“分鍾”,“小時”,“天”,“ DSTday”,“星期”,“月”或“年”之一。 可以選擇在其前跟一個(正數或負數)整數和一個空格,或后跟“ s”。
因此:
seq(df$datetime[1], tail(seq$datetime,1), by="3 hours")
# [1] "2014-04-04 09:29:00 UTC" "2014-04-04 12:29:00 UTC" "2014-04-04 15:29:00 UTC" "2014-04-04 18:29:00 UTC" "2014-04-04 21:29:00 UTC"
現在,要使序列從一個小時開始,就需要使用round
(請參見?round.POSIXt
):
round(df$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"
總而言之,您的代碼變為:
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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