Question

I have around 100 csv files with common headers, which i want to merge. The headers are “Lat”, “Long” and “value”. I am trying to merge all the csv files such that the output would be

"Lat" "Lon" "Value1" "Value2"..."Value 100" 

Lat and Lon columns are identical for all of the csv files. Merging two files is easy

merge(data.frame1, data.frame2, by=c('Lat','Lon'))

However, I tried the following code which didnt work:

file_list <- list.files(~/source)   
list_of_files <- lapply(file_list, read.csv)  
m1 <- merge_all(list_of_files, by=c("Lat","Lon"), all=TRUE)  

which throws the error

Error in merge.data.frame(dfs[[1]], Recall(dfs[-1]), all = TRUE, sort = FALSE,  : 
  formal argument "all" matched by multiple actual arguments.  

Can anyone help me in this regard.

Answer 1

You can use Reduce and the plain merge:

m1 <- Reduce(function(old, new) { merge(old, new, by=c('Lat','Lon')) }, list_of_files)