如何按组(在R，ggplot，dplyr，tidyverse中)用R编写更简单的派生? [英] How a simpler derive is written in R by group (in R, ggplot, dplyr, tidyverse)?

问题描述

在同一列中，我在y轴上有两个数据，在x轴上有一个日期时间.

我尝试为每两个数据计算数值导数，但我不理解R中的导数.(我正在寻找 stats :: D 或 diff 但这是行不通的.

f(x)=(t_n-t_n-1)/(date_time_n/date_time_n -1)

其中f(x)是我的计算列.

ie用执行此操作的函数替换下面代码中的 calc = t/10 .(我更喜欢tidyverse/dplyr)

链接

•  库(tidyverse)库(ggplot2)数据< -data.frame(t = c(50 + c(0，cumsum(runif(9，-7，7)))，70 + c(0，cumsum(runif(9，-10，10))))，orig = c(rep("s1"，10)，rep("s2"，10))，date_heure = rep(seq(from = as.POSIXct("2012-1-1 0:00"，tz ="UTC")，by ="hour"，length = 10)，2个))数据<-(数据％>％变异(calc = t/10))(ggplot(数据)+ geom_line(mapping = aes(x = date_heure，y = t，color = orig，linetype ="s1"))+ geom_line(mapping = aes(x = date_heure，y = calc，color = orig，linetype ="s2"))+ scale_y_continuous(name ="t"，sec.axis = sec_axis(trans =〜(range(datas $ calc))，name ="calc"))+ geom_point(映射= aes(x = date_heure，y =计算，color = orig)，形状= 21，填充=白色")+ scale_color_manual(name ="calc"，values = c("red"，"blue"))+ scale_linetype_manual(name ="orig"，values = c('solid'，'solid')，guide = guide_legend(override.aes = list(colour = c("red"，"blue"))))) 

  解决方案

  据我了解，您希望使用当前和以前的 t 和 date_heure 值.要获取特定列中前一行的值，可以使用 lag ，如下所示:

    datas<-(数据％>％变异(calc =(t-lag(t))/as.integer((date_heure-lag(date_heure))))) 

  请注意，第一行的 calc 值将为 NA .因此，在绘制图形之前，可能需要跳过并为其提供默认值.

  例如:

    datas<-数据[-1，]#跳过第一个`NA`值datas [1，] $ calc<-0#为它提供默认值'0' 

  希望它会有所帮助.

  I have two datas in one column by their name in y axis, and a datetime in x axis.

  I try to calculate numeric deriv for each two datas, but I don't understand derive in R. (I've looking for stats::D or diff but It doesn't work).

  f(x)=(t_n-t_n-1)/(date_time_n / date_time_n -1)

  where f(x) will be my calc column.

  ie to replace my calc=t/10, in the code below, by a function doing this. (I would prefer tidyverse / dplyr)

  Links

  • Calculate the derivative of a data-function in r
  • My previous question To add a legend by shape in ggplot ( added 2nd question after: to calculate numeric deriv)

  Below : ggplot picture of calc=t/10 where calc will be replaced by the derive.

  library(tidyverse)
  library(ggplot2)
  
  datas<-data.frame(
    t = c(
      50 + c(0, cumsum(runif(9, -7, 7))),
      70 + c(0, cumsum(runif(9, -10, 10)))
    ),
    orig=c(rep("s1",10),rep("s2",10)),
    date_heure = rep(
      seq(from=as.POSIXct("2012-1-1 0:00", tz="UTC"),by="hour", length=10) ,
      2
    ) 
  )
  
  
  datas<- (datas 
           %>% mutate (
             calc=t/10
           )
  )
  
  
  (
    ggplot(datas) 
    +   geom_line(mapping=aes(x = date_heure, y = t, color=orig, linetype = "s1"))
    +   geom_line(mapping=aes(x = date_heure, y = calc, color=orig, linetype = "s2"))
    +   scale_y_continuous(name = "t", sec.axis = sec_axis(trans=~(range(datas$calc)), name = "calc"))
    +   geom_point(mapping = aes(x = date_heure, y = calc, color=orig), shape = 21, fill = "white")
    +   scale_color_manual(name = "calc", values=c("red", "blue"))
    +   scale_linetype_manual(name = "orig", values = c('solid', 'solid'), 
                              guide = guide_legend(override.aes = list(colour=c("red", "blue"))))
  
  )
  

  解决方案

  As I understood, you want calc to be computed using the current and previous t and date_heure values. To get the value of a previous row in a particular column, you can use lag, as follows:

  datas<- (datas
           %>% mutate (
             calc = (t - lag(t)) / as.integer((date_heure - lag(date_heure)))
          )
  )
  

  Please note that the value of calc for the first row is going to be NA. Hence, you may need to skip and give it a default value before you plot your figure.

  For example:

  datas <- datas[-1,]  # To skip the first `NA` value
  datas[1,]$calc <- 0  # To give it a default value of `0`
  

  Hope it helps.

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