R iterate over group in R dataframe with for-loop

Need help with this. I have a dataframe with 3 columns as so.

date <- c(2001:2015)  countries <- c("Afghanistan", "Afghanistan", "Afghanistan","Afghanistan", "Afghanistan", "Algeria", "Algeria", "Algeria", "Algeria", "Algeria", "Albania", "Albania", "Albania", "Albania", "Albania")   value<- c(1:15)  df <- data.frame(date,country,value)  

I want to apply a function prep_plot on each unique country and add the output together in a new dataframe. I have tried a for loop as this.

data <- data.frame()  for (country in unique(df$countries)){   data1 <- prep_plot(country)   data2 <- bind_rows(data, data1)  }  

But the output (data2) only have data for Albania.

https://stackoverflow.com/questions/66847203/r-iterate-over-group-in-r-dataframe-with-for-loop March 29, 2021 at 07:42AM