使用difftime

时间：2016-05-20 02:53:22

标签： r loops row difftime

我在timefact

下有一列时间 
> head(foo)
  cnrd_marsh            timefact timefact_hour
1         БЧ 2016-04-07 14:34:00            14
2         БЧ 2016-04-07 14:15:00            14
3         БЧ 2016-04-07 14:10:00            14
4         БЧ 2016-04-07 13:58:00            13
5         БЧ 2016-04-07 13:57:00            13
6         БЧ 2016-04-07 13:39:00            13

我的目标是创建第四列，其中包含整数值，这些值表示给定行与其上方行之间的分钟数差异（difftime）。另外，我需要排除timefact_hour与上一行不同的所有情况。换句话说，我只需要找到共享相同hour的行的差异。

我能够编写以下代码，其工作原理是它从一行到下一行有所不同，但它不会将posix时间转换为字符，并且它不会跳过hour为output1 <- data.frame("timefact" = character(), diff_time = numeric(0)) for (i in 2:nrow(foo)){ diff_time <- difftime(foo[i, "timefact"], foo[i-1, "timefact"], tz = "EST", units = "mins") new_row <- c(foo[i, "timefact"], diff_time) output1[nrow(output1) + 1,] = new_row } > head(output1) timefact diff_time 1 <NA> -19 2 <NA> -5 3 <NA> -12 4 <NA> -1 5 <NA> -18 6 <NA> -31 的实例不同。 

> dput(foo)
structure(list(cnrd_marsh = structure(c(91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L), .Label = c("", "1", "10", "11", "11К", 
"12", "13", "14", "15", "16", "17", "18", "19", "1К", "2", "20", 
"21", "22", "23", "24", "26", "27", "28", "29", "3", "30", "31", 
"32", "33", "33К", "34", "34К", "35", "36", "37", "38", "39", 
"4", "40", "41", "42", "43", "43К", "44", "45", "47", "48", 
"49", "50", "51", "52", "53", "54", "55", "56", "57", "58", "59", 
"6", "60", "61", "62", "63", "63К", "64", "65", "66", "67", 
"7", "70", "70К", "71", "72", "73", "74", "76", "77", "78", 
"79", "8", "80", "81", "82", "83", "84", "85", "86", "88", "9", 
"БК", "БЧ"), class = "factor"), timefact = structure(c(1460057640, 
1460056500, 1460056200, 1460055480, 1460055420, 1460054340, 1460052480, 
1460052360, 1460051340, 1460051040, 1460050440, 1460050380, 1460049360, 
1460048160, 1460048040, 1460046960, 1460046720, 1460046300, 1460045340, 
1460045160, 1460043540, 1460042880, 1460042520, 1460041920, 1460041140, 
1460040120, 1460039760, 1460038860, 1460038620, 1460038080, 1460038020, 
1460037240, 1460036280, 1460035800, 1460034960, 1460034780, 1460034120, 
1460034060, 1460033340, 1460032500, 1460032140, 1460031300, 1460031000, 
1460030340, 1460030340, 1460029800, 1460029200, 1460028300, 1460025720, 
1460090700, 1460088660, 1460088600, 1460087760, 1460087580, 1460086980, 
1460086980, 1460086320, 1460085300, 1460085180, 1460084340, 1460084160, 
1460083620, 1460083620, 1460082780, 1460081820, 1460081760, 1460080740, 
1460080500, 1460080200, 1460079360, 1460079180, 1460077260, 1460076840, 
1460076600, 1460076360, 1460075820, 1460074740, 1460070660, 1460070480, 
1460069100, 1460068800, 1460068140, 1460068140, 1460067060, 1460063880, 
1460063460, 1460062380, 1460062080, 1460061360, 1460061300, 1460059920, 
1460057880, 1460057640, 1460060760, 1460060580, 1460059080, 1460058780, 
1460058240, 1460058180, 1460057220), class = c("POSIXct", "POSIXt"
), tzone = "EST"), timefact_hour = c(14L, 14L, 14L, 13L, 13L, 
13L, 13L, 13L, 12L, 12L, 12L, 12L, 12L, 11L, 11L, 11L, 11L, 11L, 
11L, 11L, 10L, 10L, 10L, 10L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 8L, 
8L, 8L, 8L, 8L, 8L, 8L, 7L, 7L, 7L, 7L, 7L, 6L, 6L, 6L, 6L, 6L, 
5L, 23L, 23L, 23L, 22L, 22L, 22L, 22L, 22L, 22L, 22L, 21L, 21L, 
21L, 21L, 21L, 21L, 21L, 20L, 20L, 20L, 20L, 20L, 20L, 19L, 19L, 
19L, 19L, 19L, 18L, 18L, 17L, 17L, 17L, 17L, 17L, 16L, 16L, 15L, 
15L, 15L, 15L, 15L, 14L, 14L, 15L, 15L, 14L, 14L, 14L, 14L, 14L
)), .Names = c("cnrd_marsh", "timefact", "timefact_hour"), row.names = c(NA, 
-100L), class = "data.frame")

以下是示例数据：

   > head(output)
  cnrd_marsh            timefact timefact_hour timefact_diff
1         БЧ 2016-04-07 14:34:00            14            NA
2         БЧ 2016-04-07 14:15:00            14            19
3         БЧ 2016-04-07 14:10:00            14             5
4         БЧ 2016-04-07 13:58:00            13            NA
5         БЧ 2016-04-07 13:57:00            13             1
6         БЧ 2016-04-07 13:39:00            13            18

我想问一下如何修改代码以获得正确的输出。以下是输出应该是什么样子的示例

05-20 04:17:52.955 4266-4266/rabshet.home.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
Process: rabshet.home.myapplication, PID: 4266
java.lang.RuntimeException: Unable to start activity ComponentInfo{rabshet.home.myapplication/rabshet.home.myapplication.RecyclerViewActivity}: java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.equals(java.lang.Object)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.equals(java.lang.Object)' on a null object reference
at rabshet.home.myapplication.RVAdapter.<init>(RVAdapter.java:43)
at rabshet.home.myapplication.RecyclerViewActivity.initializeAdapter(RecyclerViewActivity.java:73)
at rabshet.home.myapplication.RecyclerViewActivity.onCreate(RecyclerViewActivity.java:37)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
at android.app.ActivityThread.-wrap11(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

2 个答案:

答案 0 :(得分：1)

这是一个可能的解决方案

library(dplyr)

#a is your data.frame

#Create leads of your timefact  & timefact_hour column
# Use ifelse to assign a value to difftime depending on if leading timefact and current timefact is equal or not

b= lead(a$timefact)

a$DiffTimes = c(NA, ifelse(a$timefact_hour[-nrow(a)] == lead(a$timefact_hour)[-nrow(a)], difftime(a$timefact[-nrow(a)], b[-nrow(a)], units = "mins",tz="EST"),NA))

> head(a)
     cnrd_marsh       timefact              timefact_hour DiffTimes
 1 <U+0411><U+0427> 2016-04-07 14:34:00            14        NA
 2 <U+0411><U+0427> 2016-04-07 14:15:00            14        19
 3 <U+0411><U+0427> 2016-04-07 14:10:00            14         5
 4 <U+0411><U+0427> 2016-04-07 13:58:00            13        NA
 5 <U+0411><U+0427> 2016-04-07 13:57:00            13         1
 6 <U+0411><U+0427> 2016-04-07 13:39:00            13        18

答案 1 :(得分：0)

最简单的方法可能就是使用这样的data.table。

编辑：由于timefact_hour的混淆，通常的分组会产生意想不到的结果。因此，我们可以事先添加i过滤器，以检查timefact_hour是否发生了变化。第一个[是为timefact创建滞后变量以协助diff_time计算。如果需要，可以在之后将其删除。

require(data.table)
setDT(foo)
foo[, lag.timefact := shift(timefact)][which(timefact_hour-lag(timefact_hour)== 0), diff_time := difftime(lag.timefact, timefact, tz = "EST", units = "mins")]
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