R 的同比百分比变化 [英] year-over-year percentage change in R

问题描述

虽然我发现了几个类似的问题，但我无法在基础 R 中找到解决我的问题的简单方法.我想从一组数据(此处为 y 值)计算 yoy 百分比变化，并将此Delta"系列作为新列添加到我的数据框中.

though I have found several similar questions, I could not find a simple solution to my problem in base R. I want to calculate the yoy percentage change from a set of data (here the y value) and add this "Delta"-series as a new column to my data frame.

例如:

>x = c(2000,2001,2002,2003,2004,2005,2006)   
>y = c(100,104,106,108,112,115,121)   
>df = data.frame(x,y)

如果我通过读取 .csv 文件加载数据该怎么办?我是否必须将此数据转换为数据框?

And what to do if I load my data by reading a .csv file? Do i have to convert this data to a data frame?

推荐答案

data.table_1.9.5 引入了新函数 shift，默认为 type='lag' 和 n=1L.如果需要更改，您可以指定这些参数.setDT 将 data.frame 转换为 data.table，基于标准 (y/shift(y)...)

data.table_1.9.5 introduced new function shift, which by default will be type='lag' and n=1L. You could specify those arguments, if you need to change. setDT converts data.frame to data.table, a new column is created (:=) based on the criteria (y/shift(y)...)

library(data.table)
setDT(df)[, new.col := y/shift(y) - 1]

或者在基础 R 中(来自@David Arenburg 的评论)

Or in base R (from @David Arenburg's comments)

transform(df, new.col=c(NA,y[-1]/y[-nrow(df)]-1))

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