Plot two large Raster Data Sets in a Scatter Plot

Question

i have a problem with plotting two Raster Data Sets in R.

I use two different IRS LISS III Scenes (with the same Extent) and what i want is to plot the pixel values of both scenes in one Scatterplot (x= Layer1 and y=Layer2). My problem is now the handling of the big amount of data. Each Scene has about 80.000.000 pixels due reclassification and other processing i was able to scale down the values to a amount of 12.000.000 in each raster. But when i try to import these values e.g. in a data.frame or load them from an ascii file i always got problems with my memory. Is it possible two plot such an amount of data, and when yes it would be great if someone could help me, i was trying it for two days now and right now im desperated.

Many thanks,

Stefan

Answer 1

Use the raster package, there's a good chance it will work out of the box since it has good "out-of-memory" handling. If it doesn't work with the ASCII grids, convert them to something more efficient (like an LZW-compressed and tiled GeoTIFF) with GDAL. And if they are still too big resize them, that's all the graphics rendering process will do anyway. (You don't say how you resized originally, or give any details on how you are trying to read them).