[R] Tidyverse data frame conversion from monthly to annual

[Amit Mittal]

Try using time series objects in xts. Should be easy. At worst once the xts object is automatically arranged by date you have to note the row numbers for each year period and I think data would be ok to handle unless it is more than 30-40 years when you would look up other xts options. Xts objects would automatically take the date column and use them as row ids so there is obviously another simple loop you can generate for summing up . There would also be easy functions once you start with xts. 


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From: phil using philipsmith.ca
Sent: 04 March 2019 08:45
To: r-help using r-project.org
Subject: [R] Tidyverse data frame conversion from monthly to annual

I have a data frame in which the first column is a sequence of monthly 
dates and the other columns are variables. There are a great many 
variables. I want to create another data frame similar to the first one, 
but with annual values instead of monthly, created by summing the months 
within each year.

I am able to do this as shown in this reprex:

library(tidyverse)
REF_DATE <- seq(as.Date("2000/1/1"),by="month",length.out=36)
set.seed(57)
df <- data.frame(REF_DATE,
                  x=sample(1:100,size=36),
                  y=sample(1:100,size=36),
                  z=sample(1:100,size=36),
                  Year=year(REF_DATE))
df1 <- df %>%
   group_by(Year) %>%
   summarise(x_a=sum(x),y_a=sum(y),z_a=sum(z)) %>%
   ungroup()

However, while this works for the simple case with only three variables, 
I actually have many more than three, so I am looking for a more general 
approach. I have no clue as to how to proceed. Any advice will be much 
appreciated.

Philip

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