Correlation between Rasters? Raster Validation?

[KathrinSchulte-Braucks]

Hey,

I have several raster files which I'd like to analyze concerning their level of similarity / correlation. What's the best way doing this? Apparently, Geostatistical Analyst only works with Vector Data. So do I have to apply the formula manualy with Map Algebra or is there a predefined tool e.g. for Pearson correlation or cross validation of raster files?

Thanks,

Kathrin

[EricKrause]

I think you want the Band Collection Statistics tool in Spatial Analyst.  It takes rasters as input and can output the correlation matrix (among other statistics).  Just make sure to check the "Compute covariance and correlation matrices" box.

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z000000p5000000.htm

[Devon_Reid]

Hallo Eric, I see this is from a looong time ago, however it is useful in what I'm doing now (unless there are better ways to test for collinearity now).  I am preparing raster surfaces for a maxent model, and have calculated the correlation matrix.  One question - is this Person's? It looks exactly like it for a group sample.
thanks,

Devon

[KathrinSchulte-Braucks]

Hello Eric,

thank you very much for your answer, it really helped me a lot.

This is exactly what I was looking for!

Kathrin

[KathrinSchulte-Braucks]

Hello,

is it somehow possible to calculate the statistical significance of the correlation values contained in the correlation matrix within ArcGIS?

Thank you very much,

Kathrin

[KathrinSchulte-Braucks]

Any suggestions? Anyone? 😉

I'm comparing different raster files, some of them with different resolution. I'd like to find out how they correlate and how significant this correlation is.

Raster Band Statistics works so far, but I don't know how to compute the significance of the results with ArcGIS. Is it possible to calculate correlation and significance maybe with SPSS for grids?

Another problem occured: When comparing rasters with different cell size, some rasters get wrong MIN, MAX and STD values. So I first resize all grids to the cell size of the most detailed grid, and then compare, then the MIN, MAX and STD values are okay.

But since I have different resolutions, the amount of cells differs, so I can't just compare the VATs. I have somehow to account for the area. Would it helpful to resize the coarse grids to the same cell size as the grids with the best resolution and then compare the VATs with Excel? But how do I compute signifance and correlation in Excel or SPSS for a VAT which does not list each single value but only the count of each value?

[KathrinSchulte-Braucks]

Okay, found my own solution:

Convert Rasters to Points, copy all Gridcode Columns into one table, open this table with R and calculate correlation coeff. and significance / regression in R. This works.

[EricKrause]

You could also convert the rasters to points, join the points by location, and run the Ordinary Least Squares tool in Spatial statistics.  Testing the significance of the coefficient in the linear model is the same as testing the correlation.

[KathrinSchulte-Braucks]

Thank you again, Eric!

I'll try that out. I came across OLS before, but since I only have ArcView, I did not find the OLS Tool. Since I do have the Spatial Analyst Extension I do have access to OLS, when I uncheck "Hide Locked Tools". I somehow overlooked this in the Tool Help.

[CarlosSarmiento1]

Your conversation has helped me a lot. I have exactly the same problem as Katherine had. Thanks you both.