Loop over dataframes and extract specific values to generate multiple rasters/plots

Question

I would seek help to revise this script. I need to generate multiple plots.

For example, the following code works well ggplot and gsave but I would prefer to use raster, and I tried something such as above, but I am new with this package/library

      setwd ('~/Documents/test')
      file_list <- list.files(path='~/Documents/test')
      filenames <- gsub('\\.dat$','', list.files(pattern='\\.dat$'))
   
      for(i in filenames){
      df <- read.table(paste(i, '.dat', sep=''))
      pl = ggplot(df, aes(x = V2, y = V3, color = V5)) + 
      geom_point(shape=22,size=3,alpha = 1,na.rm=TRUE,aes(fill=V5))+  
      #scale_color_continuous(low = 'blue', high = 'red')  
      ggtitle('Temperature - 2010-2020') +
      ggsave(plot = pl, filename = paste0('tp_', i, '.png'))
      }
 

################################### second option with 'Raster'

       
        for(i in filenames){
        df0 <- read.table(paste(i, '.dat', sep=''))  
        e <- extent(150,200,150,200)
        r <- raster(e, ncol=10, nrow=20)
        x <- rasterize(df0[,2:3], r, df0[,5], fun=mean)  
        rass <- writeRaster(x, filename[i])  ' ## This line (ras) cause the error
        }


 I got the error- Error in h(simpleError(msg, call)) : 
  error in evaluating the argument 'filename' in selecting a method for function 'writeRaster': object of type 'closure' is not subsettable

# Using GNU R Version 4.0.2.