Convert a dataframe whose row name is month and column name is year to a time series object using R

Say I have an excel file with format like this (to download from this link):

Note the first column is year and the first row is month.

I try to convert it to time series object then draw a seasonal plot using ggseasonplot or ggplot2.

df <- openxlsx::read.xlsx('dataset1.xlsx', sheet='Sheet1', colNames=TRUE, rowNames = TRUE)
# df <- t(df)
df <- ts(df, start = c(2008, 1), end=c(2021, 12), frequency = 12)
forecast::ggseasonplot(df, col=rainbow(12), year.labels=TRUE)

Output:

Error in data.frame(y = as.numeric(x), year = trunc(round(time(x), 8)),  : 
  arguments imply differing number of rows: 2352, 168

How could I do that correctly using R? Thanks in advance.

References:

https://pkg.robjhyndman.com/forecast/reference/seasonplot.html

https://afit-r.github.io/ts_exploration

>Solution :

If it is a continuous time series, then you can drop the month column and put all years into one column (and also remove the year after using melt). Then, you can just specify your start year and month.

output <- ts(reshape::melt(df[,-1])[,2], start = c(2008, 1), frequency = 12)
forecast::ggseasonplot(output, col=rainbow(12), year.labels=TRUE)