for loop with mutate only outputs last result

I'm sorry if it's a duplicate, and for the lack of reproducibility, I'd have to link you the files.

What I'm trying to do is this:

I have a data frame with coordinates and names, let's say

df <- tribble(
  ~Species, ~lat, ~lon,
  "a",42.92991, 11.875801,
  "b",42.92991, 11.875801,
  "c",43.91278, 3.513611,   
  "d",43.60851, 3.871755,   
  "e",39.24373, 9.120478
)

I also have a folder with tifrasters, such as

files <- list.files(path="~/world/", pattern="*.tif$", full.name=TRUE, all.files=TRUE)

Now for each iteration I'd like to:

create a new column on the data frame with the file name
insert in that column the extracted value for the corresponding lat and lon

I've tried using this for loop, and while on paper looks just fine, I don't understand why it outputs to funvar the last result only. I't like it overwrites the result instead of appending it.

If I use a similar loop with mutate and simpler objects, it appends them, so I'm not sure what the problem could be

for(i in files){  
fraster<- raster(i)

fname<-gsub(".*//|[.].*", "", i)

funvar<-dplyr::mutate(fundata, !!fname:= raster::extract(fraster, coordinates(data.frame(lat,lon))))
}

Thanks!

Solution

The way I solved it is a bit of an hack, but works. I explicitly assign the new column to a data frame, like this. I'm still notsure why mutate doesn't do that by itself

for(i in files){  
fraster<- raster(i)

fname<-gsub(".*//|[.].*", "", i)

funvar<-dplyr::mutate(fundata, !!fname:= raster::extract(fraster, coordinates(data.frame(lat,lon))))

fundata[fname] <- funvar[[fname]]
}