nav[aria-label="Primary Navigation"] { padding: 0; & ul { list-style: none; width: 100%; display: flex; flex-direction: row; justify-content: start; align-items: start; gap: 30px; padding: 0; & li { margin: 0; } & ul li { list-style: none; } } }

How to concatenate raster images in one representing value?

AshrafAfana

Hi all,

I'm trying to concatenate the values of two raster images in order to have a value that includes both of them (e.g. 02 + 07 = 0207). I'm trying to use the following in Raster Calculator "image1" & "" & "image2" but with no success.

any suggestions?

Finde mehr Beiträge mit dem Tag

Accepted answers

SteveLynch

have a look at Combine

All comments

IanMurray

Do your rasters have the same extent and cell size?

ChrisDonohue__GISP

Not sure if this will take you where you want to go, but I will throw it out there:

If 0207 is the desired output of rasters with values of 02 + 07, try multiplying the first raster by 100 before adding the raster values together.

Essentially: (02*100) + 07

Chris Donohue, GISP

DanPatterson_Retired

Rasters are represented by numbers ... 02 would suggest text... you can concatenate text, but not numbers. You won't get a preceeding 0 in 0207, the closest you will get is 207 as suggested by Chris. Your end goal is therefore confusing

SteveLynch

have a look at Combine

AshrafAfana

Yes. Same resolution and same extension.

AshrafAfana

Thanks Chris for the reply and for the simple idea. This should work with me. I thought ArcGIS can do it by converting the numbers to string character and concatenate them.

Thanks

AshrafAfana

Thanks Dan,

Absolutely agree, but I was using R where I can convert numeric to string character and concatenate them and I thought if there was away to do it directly in ArcGIS. Anyway, Chris suggestion was a valid solution.

Thanks

AshrafAfana

Thanks Steve,

But combine does not solve my problem.

curtvprice

Raster datasets in ArcGIS do not contain strings for each cell, natively, the values in the raster are numbers. When there is a string value for a cell it is stored in a raster attribute table related to each value. (Only integer rasters can have such a table.)

I disagree, I believe Steve Lynch is right on (as usual, Hi Steve) in suggesting Combine(): this is a more general solution as you could then a build a Calculate Field expression to populate a string field in the raster table with something that you want like "0207". One could do other encodings (to strings or numbers) by using a different Calculate Field expression.

1. Combine("ras1", "ras2")

The output will raster table will have two fields, RAS1 and RAS2, with a row for every unique combination (not every cell) and a COUNT of how many had that combination.

2. Add Field, "RCODE", "TEXT"

3. Calculate Field Python expression: "{:02}{:02}".format(!RAS1!, !RAS2!)

The RCODE field will be set to "0207" if RAS1=2 and RAS2=7 for that row.

DanPatterson_Retired

way too much overkill for a preceeding zero

far easier to edit the legend

AshrafAfana

This is a tricky but genius answer and it solves the problem in a handy way. To be honest, I coded the process in python and it works for as many combination as you'd like. Thanks Curtis.

Ashraf

AlysKarimi

Hi Ashraf,

I have a similar issue with concatenating Fields of rasters in ArcMap. I combined 2 rasters to get a raster with both Fields from the 2. Then I concatenated the text Fields as per the suggestions above. The result is fine. But the problem with this raster is that when I apply Raster Calculator, it does not work on the joint fields, and it only works on the Value and Count fields. I was thinking you might have encountered the same issue and could give me some advice.

Cheers.

curtvprice

You can access raster fields using the Lookup tool. Not so sure you can apply Raster Calculator on text values however.

AlysKarimi

Thanks Curtis.

That's actually really helpful. I did not know about this tool at all. But I am wondering wouldn't the "join from a table" do the same thing?

curtvprice

But I am wondering wouldn't the "join from a table" do the same thing?

Lookup is the way to access fields in raster attribute tables that are not value. In 9.x the syntax for this was 'raster.field' (eg 'raster.COUNT') this is now in map algebra expressed as Lookup(raster, "COUNT") If you have a active join from the raster table to another table, you can use that in the Lookup expression with the fully qualified field name in the joined table: Lookup(raster, "othertable.field")

Again in map algebra expressions must resolve to a numeric value -- you can't use map algebra to combine raster table text fields. The best you can do to combine text fields from multiple raster inputs is do a Combine, add a new text field to the Combine output raster table, add a join back to the inputs using Add Join and run Calculate Field to populate the new field from calculations using the fully-qualified related field names.

Nimm an der Diskussion teil

Angemeldete Mitglieder können Beiträge verfassen, Updates folgen und mehr. Neu hier? Registriere ein kostenloses Konto.

Schnellzugriffe

Community Help
Find useful guides, FAQs, and documents to help you navigate and make the most of Esri Community.