How to change unique values limit from 65536 in ArcGIS Pro?

[q1azza]

Hey everyone. I'm new to ArcGIS Pro and I've been following along an edX course on spatial analysis. Specifically, it teaches how to use bands to determine vegetation health. Anyhow, when I go to change the primary symbology to "Classify" on the ndvi layer I get this message: "The number of unique values in your data is greater than the set limit (65536). Edit the Maximum number of unique values to display, within the Raster and Imagery Options." In addition, the option boxes are empty.

I've tried what it suggests, going to the Raster and Imagery options, but it lacks details. There's also no attribute table for the layer. Help a newbie out?

If this has been answered before please point me to the right direction as I could not find one.

[DuncanHornby]

Firstly there is no attribute table as NDVI data is typically a non-integer raster, i.e. it is float 32 and such rasters do not have an attribute table. Don't know what the difference between integer and float is? Go Google that.

Classify is failing to run because unsurprisingly your float raster exceeds the default limits. In this case go to the options and change it, but what to? Doesn't matter chuck a bunch zeros after the number, I show what I did for my float raster below.

Go back to your symbology Pane, you will have to change Primary symbology dropdown to something else then back to Classify and hey presto it all starts to work. If it fails go back and add more zeros.

[DanielStratten]

The surprising thing is that the application would even evaluate unique values in a floating point raster. Yes, changing the max unique value # can resolve the error, as has been discussed in earlier posts. But the error is a bug, and ESRI should resolve it. 

[WRingle]

I have a related post on this. What I eventually ended up doing was writing a short arcpy script to reclassify the raster, with the only input being the defined interval - what the ESRI symbology tool should be doing. The minimum and maximum values are parameters contained in the raster, so using those, the number of intervals can easily be calculated.

[TylerCowdreyWADNR]

Has anyone gotten any acknowledgement from ESRI that this recent behavior change was or was not intended? @DuncanHornby 's suggestion worked but I work with very large floating point rasters (often on the order of 10s of GB for a single .tif) and now I have to watch ArcGIS "Generating unique values" for minutes on end every time I switch between stretch and classify.... I don't remember this ever being an issue before the 3.3.x patches.

[willbruce_KarukTribeDNR]

Agreed, this is a bug. Looks like it's schedule for a fix: Solved: Can’t display classified raster in ArcGIS Pro 3.3 - Esri Community

[TS4]

Great to know this is being fixed, but what an embarassing bug to let slip through the cracks. Such basic functionality.

[TylerCowdreyWADNR]

Thank you for linking to that! I'm very glad they are fixing this soon.

[willbruce_KarukTribeDNR]

No prob! Also, the fastest workaround I've found is to import symbology from any layer that already is symbolized via "Classify" onto the layer you want to symbolize. This will skip the hanging "Generate Unique Values" screen. You can change the method/class breaks/ramps afterwards.