Question

我的数据框格式如下：

df$timestamp <- as.POSIXct(df$timestamp,format="%Y-%m-%d %H:%M:%S", tz="America/New_York")

我将时间戳转换为POSIX 的方式如下：

                    timestamp             value    
2014-02-14 14:27:00 "2014-02-14 14:27:00" "51.8460"
2014-02-14 14:32:00 "2014-02-14 14:32:00" "44.5080"
2014-02-14 14:37:00 "2014-02-14 14:37:00" "41.2440"
2014-02-14 14:42:00 "2014-02-14 14:42:00" "48.5680"
2014-02-14 14:47:00 "2014-02-14 14:47:00" "46.7140"
2014-02-14 14:52:00 "2014-02-14 14:52:00" "44.986"

之后，当我打印数据框的内容时，它似乎是这样的：

  df <- read.csv(csv_filename, stringsAsFactors=FALSE)
  df$timestamp <- as.POSIXct(df$timestamp,format="%Y-%m-%d %H:%M:%S", tz="America/New_York")
  s <- xts(df, order.by = df$timestamp) #time series conversion

我正在使用的代码：

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';
import 'rxjs/add/operator/map';

@Injectable()
export class SwPeopleService {
    people$ = this.http.get('https://swapi.co/api/people/')
      .map((res:any) => res.results);

    constructor(private http: HttpClient) {} 
}

我不确定为什么xts函数会复制时间戳。

Answer 1

通常（通常是？），时间序列在向量上。完成data.frame后，它会以静默方式转换为matrix，在这种情况下，会导致所有内容都转换为character（即使是POSIXct）。

str(xts(df, order.by=d$timestamp))
# An 'xts' object on 2014-02-14 14:27:00/2014-02-14 14:47:00 containing:
#   Data: chr [1:5, 1:2] "2014-02-14 14:27:00" "2014-02-14 14:32:00" "2014-02-14 14:37:00" ...
#  - attr(*, "dimnames")=List of 2
#   ..$ : NULL
#   ..$ : chr [1:2] "timestamp" "value"
#   Indexed by objects of class: [POSIXct,POSIXt] TZ: America/New_York
#   xts Attributes:  
#  NULL

（请注意，数据为chr或character。）

相反，请使用xts(df$value, order.by=df$timestamp)，因为它会保留数字类：

str(xts(df$value, order.by=df$timestamp))
# An 'xts' object on 2014-02-14 14:27:00/2014-02-14 14:47:00 containing:
#   Data: num [1:5, 1] 51.8 44.5 41.2 48.6 46.7
#   Indexed by objects of class: [POSIXct,POSIXt] TZ: America/New_York
#   xts Attributes:  
#  NULL

列中的时间戳重复;重复预期？

1 个答案: