在 R 中循环指定文件名（converting.nc to geotiff）

Question

I have a folder of.nc files on sea surface temperature, and I have a loop which extracts the variable I want ("analysed_sst") from the.nc file and writes the files to rasters. I want to specify the name of the outputted raster files to be the first section of the original.nc file (which is the date).

An example would be that the original.nc file is called "20220113090000-JPL-L4_GHRSST-SSTfnd-MUR25-GLOB-v02.0-fv04.2.nc" and so I would like the outputted raster to be called "20220113_STT.tiff". I've attached the loop I'm using below.

library(ncdf4)
library(raster)
   
#input directory
dir.nc <- #file path

files.nc <- list.files(dir.nc, full.names = T, recursive = T)

#output directory
dir.output <- #file path

#loop 
for (i in 1:length(files.nc)) {
  r.nc <- raster(files.nc[i])
  writeRaster(r.nc, paste(dir.output, i, '.tiff', sep = ''), format = 'GTiff', overwrite = T)
}

Answer 1

dirname() is vectorized so you should be able to safely use dirname(files.nc) to get the directory for each file.

Side note: It can be safer to use seq_along(files.nc) rather than 1:length(files.nc) . When length(files.nc) == 0 you can get some confusing errors because 1:0 produces [1] 1 0 and your loop will try to do some weird stuff.