I have temperature as a raster file and different ecoregions of a province as polygons.
What I want to do is calculate the mean temperature per ecoregion.
I succeeded in doing this by Zonal Statistics which creates an output raster, but what I actually want, as I realized later, is I the temperature value per ecoregion. So how do I assign that value to the ecoregion?
I thought I can do zonal statistics as table and then join this table to the ecoregion.
It does work but for some reason it does not calculate values for some of the ecoregions (1400 ouf of 7400 get null values). I tried to find a pattern in the ecoregions that didn't get assigned a value, so e.g if they were too small or have a too complicated shape or if they are at the edge of the province…but no..they are just randomly distributed.
Any ideas or something that I am missing?
Best Answer
I took a look at the data you provided. Initially, I had issues getting ArcMap to recognize the ASCII raster format. I had to open the ascii file in Notepad++ and rename it as a .asc file instead of .ascii. Once I got it into ArcMap, I had projection issues. I was able to get everything working properly by reprojecting the .asc raster to another projection (it shouldn't matter which projection you use, I used CA Teale Alber's just because that's what I use for work, but you should use one that makes sense for the area). In the process of reprojecting the data, it converted the raster from ascii to a .img. Using the newly reprojected .img raster as an input, I had no issues with NoData appearing in my zonal statistics raster or table (I ran both tools).
I suspect that this is a format issue that may relate to the projection file included with the .ascii raster. Try reprojecting the ascii file (and in the process converting it to a .img) and using that as an input and see if that works for you.