Converting Monthly Data to Daily in R

Question

I have a data.frame df that has monthly data:

Date           Value 
2008-01-01      3.5          
2008-02-01      9.5          
2008-03-01      0.1                   


        

Answer 1

An option using tidyr::expand expand a row between 1st day of month to last day of month. The lubridate::floor_date can provide 1st day of month and lubridate::ceiling_date() - days(1) will provide last day of month.

library(tidyverse)
library(lubridate)

df %>% mutate(Date = ymd(Date)) %>%
group_by(Date) %>%
expand(Date = seq(floor_date(Date, unit = "month"),
       ceiling_date(Date, unit="month")-days(1), by="day"), Value) %>%
as.data.frame()

#          Date Value
# 1  2008-01-01   3.5
# 2  2008-01-02   3.5
# 3  2008-01-03   3.5
# 4  2008-01-04   3.5
# 5  2008-01-05   3.5
#.....so on
# 32 2008-02-01   9.5
# 33 2008-02-02   9.5
# 34 2008-02-03   9.5
# 35 2008-02-04   9.5
# 36 2008-02-05   9.5
#.....so on

# 85 2008-03-25   0.1
# 86 2008-03-26   0.1
# 87 2008-03-27   0.1
# 88 2008-03-28   0.1
# 89 2008-03-29   0.1
# 90 2008-03-30   0.1
# 91 2008-03-31   0.1

Data:

df <- read.table(text = 
"Date           Value 
2008-01-01      3.5          
2008-02-01      9.5          
2008-03-01      0.1",
header = TRUE, stringsAsFactors = FALSE)