for(n in imgList){
      masked = mask(n, masky)

      unsup=unsuperClass(masked, nClasses=2)
      plot(unsup$map, col=sample(colors(), 2))

      setwd("C:/Users/tuf04002/Documents/ARSfinal/class")
      writeRaster(unsup, filename= paste(n, "unsup", sep="_"), format="GTiff", overwrite=TRUE)
    }

Error in (function (classes, fdef, mtable)  :
  unable to find an inherited method for function ‘mask’ for signature ‘"character", "SpatialPolygons"’