Doing a join in ArcMap when there's no attribute table

Question

I'm trying to do a join between two datasets in ArcMap (version 10.4.1), but haven't found a way to do it. The first is a map of U.S. states that I got from ArcGIS Online (cb_2016_us_state_5m). The second is the PRISM rainfall data downloaded from http://www.prism.oregonstate.edu/recent/ in ASCII format (I've also tried the bil files). I opened the states data first and then PRISM, and they are using the same projection. Basically, I'd like to be able to use R to average the rainfall over various states so my goal is to produce a csv file which lists every grid cell with the state that it belongs to (either name or STATEFP code).
I've done this before with other precipitation datasets, but the problem here is that neither the ASCII or .bil PRISM data has an attribute table, so I don't see how I can do a spatial join on it. But I've tried a few options.

• The "join" option is grayed out when you right click on the PRISM ascii in the TOC.
• I converted my ascii file to a layer and then tried to use the "Add Join" tool from the tool box. However, I get an error that says the dataset must be a feature layer. Bizarrely, when I tried to use the "Make a feature layer" tool, I got an error that the input I gave was not a feature layer.
• I've tried converting it to a raster (ASCII to Raster tool) hoping that that would produce an attribute table, but I get a syntax error about a comma (but there's no commas in the ASCII file).

Note that I don't have a spatial analyst license (working on getting one, but it'll be awhile). Some solutions I've seen online use those tools, so I'd like an alternative if anyone can give one.

Thanks for any help you can give.

Answer 1

I am a little confused by your question. Are you trying to get one average value for an entire state or do you want all values for all pixels within a state?

If you want the PRISM data to have attribute values to link to, you can use ratify in the Raster package. Or you could convert your raster file to a spatial grid then a vector which will create an attribute value based on the grid cell value and then do an intersect with the states layer to add the state name.