cleaning up and testing

spatial subsampling function and random sampling

initial commit for spatial subsampling code for NEX tile with many stations

run6 assessment NEX part2: generating raster map of accuracy and number of stations

run6 assessment NEX part2: adding new functions to generate raster map of accuracy overall and daily

run6 assessment NEX part2: add new plots of assessment of first global run

run6 assessment NEX part1: first global run with specific k

run5 assessment NEX part3: modifications of function script to analyze results of tiles

run5 assessment NEX part3: running diagnostic for specific tiles for more in depth analyses

run5 assessment NEX part1: adding functions to recreate raster object for assessment