根据年份合并data.frames并填写缺失值 [英] merge data.frames based on year and fill in missing values

问题描述

我有两个要合并在一起的data.frame。第一个是：

I have two data.frames that I want to merge together. The first is:

datess <- seq(as.Date('2005-01-01'), as.Date('2009-12-31'), 'days')
sample<- data.frame(matrix(ncol = 3, nrow = length(datess)))
colnames(sample) <- c('Date', 'y', 'Z')
sample$Date <- datess

第二个：

a <- data.frame(matrix(ncol = 3, nrow = 5))
colnames(a) <- c('a', 'y', 'Z')
a$Z <- c(1, 3, 4, 5, 2)
a$a <- c(2005, 2006, 2007, 2008, 2009)
a$y <- c('abc', 'def', 'ijk', 'xyz', 'thanks')

我希望合并后的年份与年份匹配，然后为每个年份填写其余的值那年的一天。

And I'd like the merged one to match the year and then fill in the rest of the values for every day of that year.

Date          y      Z
2005-01-01   abc     1
2005-01-02   abc     1 
2005-01-03   abc     1
{cont}
2009-12-31   thanks  2

推荐答案

您可以使用 match

matched<-match(format(sample$Date,"%Y"),a$a)
sample$y<-a$y[matched]
sample$Z<-a$Z[matched]

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