将R中的数据帧变换为单独列的简单方法 [英] Easy way to transform data frame in R - one variable values as separate columns

问题描述

我有什么（显然我提供了我目前数据的一小部分）：

What I have (obviously I'm presenting a very small fraction of my current data):

my_df <- structure(list(X = structure(c(48.75, 49.25), .Dim = 2L), Y = structure(c(17.25, 17.25), .Dim = 2L), Time = structure(c(14625, 14626), .Dim = 2L, class = "Date"), spei = c(-0.460236400365829, -0.625695407390594)), .Names = c("X", "Y", "Time", "spei"), row.names = 1:2, class = "data.frame")

我需要什么：

new_df <- structure(list(X = structure(c(48.75, 49.25), .Dim = 2L), Y = structure(c(17.25, 17.25), .Dim = 2L), "2010-01-16" = c(-0.460236400365829, NaN), "2010-01-17" = c(NaN, -0.625695407390594)), .Names = c("X", "Y", "2010-01-16", "2010-01-17"), row.names = 1:2, class = "data.frame")

最简单的方法是什么？
我想过要写一个for循环，但是我猜应用/ sapply可能有帮助吗？

What is the easiest way of doing this? I thought about writing a for loop, but I guess that apply/sapply might help on this?

推荐答案

您可以使用库 tidyr 及其传播这样的功能：

You can use library tidyr and its spread function like this:

library(tidyr)
spread(my_df, Time, spei)
      X     Y 2010-01-16 2010-01-17
1 48.75 17.25 -0.4602364         NA
2 49.25 17.25         NA -0.6256954

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