This question arose from these exercises.

I never use ArcGIS before. What’s the limitation of R which ArcGis can do but R can’t? And what else R can do in this area except loading area map?

Well, the things we have done in R barely scratch the surface of what can be done in R with spatial data. So lots. The relationship of ArcGIS to R is a bit like the relationship of Excel to R. You can do alot with clicking in dialogs in ArcGIS that require you to write code in R. But then the code clearly documents what you did, and you can repeat it quickly and easily. I believe ArcGIS uses Python in the same way that Excel uses Visual Basic – so you can code in ArcGIS if you want to.

Are there things you can do in ArcGIS that you can’t do in R? I don’t know – not a GIS expert. But there are certainly things you can do better in R than ArcGIS. For statistical modeling of spatial data you generally export data from ArcGIS to R, then do the modelling. Export the results back to ArcGIS for making the map. But you can do all of that data extraction and mapping directly in R, you just have to write code to do it. At least one student I know gave up using ArcGIS to just use R for spatial data after learning some of these tools.

Another student added this:

I’ve been using Arcmap in order to process UAS+sensor-derived imagery.

Although I haven’t tried processing them in a similar fashion in R, one thing that I do in Arc and I have no idea of how could be made in R is to georeference an image using ground control points.

For that, it is handy to be able to click on your map, and I’m not sure if R gives you this interactivity.

Also, when drawing plot boundaries in Arc, it is essential to be able to interact with the image by clicking. Again, not sure if R would offer this feature or a way around it.

Short answer: locator()

Longer answer: Both of those tasks are essentially data entry, and just like with regular data entry you don’t really want to do it in R even though you can. Somewhere between 3 and 10 numbers it becomes much, much more efficient to use something like an Access form or Excel to enter numbers. I imagine the same is true of images and digitizing points and polygons.

I’d love to hear other reasons for using ArcGIS. If you have an example, tweet or send me an email.