Reformatting downloaded Excel data - r

Question

I have downloaded some GDP data in .xls-format from the OECD website. However, to make this data workable in R, I need to reformat the data to a .csv file. More specifically, I need the year, day and month in the first column, and after the comma I need the GDP values (for example: 1990-01-01, 234590).
The column with GDP values can be easily copied and transposed, but how does one quickly add dates? Is there a fast way to do this, without having to add in the dates manually?
Thanks for the help!
Best,
Sean
PS. Link to (one of) the specific OECD files: https://ufile.io/8ogav or https://stats.oecd.org/index.aspx?queryid=350#
PSS. I have now changed the file to this:
Which I would like to transform into the same style as example 1.
Codes that I use for reading in data:
gdp.start <- c(1970,1) # type "double"
gdp.end <- c(2018,1)
gdp.raw <- "rawData/germany_gdp.csv"
gdp.table <- read.table(gdp.raw, skip = 1, header = F, sep = ',', stringsAsFactors = F)
gdp.ger <- ts(gdp.table[,2], start = gdp.start, frequency = 4) # time-series representation
PSS.
dput(head(gdp.table))
structure(list(V1 = c("Q2-1970;1.438.810 ", "Q3-1970;1.465.684 ",
"Q4-1970;1.478.108 ", "Q1-1971;1.449.712 ", "Q2-1971;1.480.136 ",
"Q3-1971;1.505.743 ")), row.names = c(NA, 6L), class = "data.frame")

Answer 1

Using your data:
z <- structure(list(V1 = c("Q2-1970;1.438.810 ", "Q3-1970;1.465.684 ",
"Q4-1970;1.478.108 ", "Q1-1971;1.449.712 ", "Q2-1971;1.480.136 ",
"Q3-1971;1.505.743 ")), row.names = c(NA, 6L), class = "data.frame")
dat <- read.csv2(text=paste(z$V1, collapse='\n'), stringsAsFactors=FALSE, header=FALSE)
dat
# V1 V2
# 1 Q2-1970 1.438.810
# 2 Q3-1970 1.465.684
# 3 Q4-1970 1.478.108
# 4 Q1-1971 1.449.712
# 5 Q2-1971 1.480.136
# 6 Q3-1971 1.505.743
and a simple function to replace quarters with the first date of each quarter
quarters <- function(s, format) {
qs <- c("Q1","Q2","Q3","Q4")
dts <- c("01-01", "04-01", "07-01", "10-01")
for (i in seq_along(qs))
s <- sub(qs[i], dts[i], s)
if (! missing(format))
s <- as.Date(s, format=format)
s
}
We can change them into strings of dates, preserving the order:
str(quarters(dat$V1))
# chr [1:6] "04-01-1970" "07-01-1970" "10-01-1970" "01-01-1971" ...
or we can convert into Date objects by setting the format:
str( quarters(dat$V1, format='%m-%d-%Y') )
# Date[1:6], format: "1970-04-01" "1970-07-01" "1970-10-01" "1971-01-01" ...
so replacing the column with the actual Date object is simply dat$V1 <- quarters(dat$V1, format='%m-%d-%Y').