R: writing the data related to each unique occurence into a separate file using for loop

I am a beginner to coding in R. I have 60 unique ID's in a column with each unique ID having 30 entries, I would like to write a code which automatically creates separate files for each unique ID. This code worked for a single ID

unique(src$ID)
ID2<- subset(src, ID=='099857')
write.csv(pat2,file= "D:/R/ID2.csv")

when I try to loop it using the following code.

for (i in 1:length(unique(src$ID)))
{ unique(src$ID)
  id<- subset(src, ID== "i")
  paste(id)
  write.csv(i,file="D:R/i.csv")
}

I get a file that just counts all the unique IDs (60) and pastes them into an excel sheet.

trying to incorporate the structure for a single ID into an automated loop.

expected output- 60 unique files with 30 entries each.

Does anybody have any suggestions? Thank you.

Solution

You are iterating over a numeric vector (1:length(unique(src$ID)), but in the loop you refer to i as a character vector "i". Try changing it to:

for(i in unique(src$ID)) {
ID2 <- subset(src, ID == i)
write.csv(ID2, file = paste0("D:/R/",i,".csv"))
}

...if the name of the column that contains the ID is "SampleID," then you should change it to:

 for(i in unique(src$SampleID)) {
    ID2 <- subset(src, SampleID == i)
    write.csv(ID2, file = paste0("D:/R/",i,".csv"))
    }