I am trying to set up a Graphab project and to calculate a linkset. This works fine when using a small crop of the original research area with an external raster file containing resistance values, or when assigning some class-specific resistance values. However, when I use the full extent of the map in combination with an external raster file that contains the resistance values, I get the following error:
"java.lang.RuntimeException: java.lang.IllegalStateException: Negative or null cost is forbidden. Check your cost."
There are no null or negative values in the resistance raster, so what shall I make of this message? Could it have been caused by some other issue not accurately reflected in the error message?
Turns out, theraster I got actually contained a negative value as the NoData value, which, however, was recognized as no data by R and GIS programms, with the exception of Graphab.
Hi Manuel, thank you for answering your own question, I am having the same trouble, but in my case the map had no negative values nor null values, what worked was converting the raster as a factor before saving it for graphab. Adding my code here in case anyone runs into similar issues.
resistance_file1
Update: my previous answer works because it pushes all values >=1, this can be achieved without converting it to factor by simply adding a 1 to your values. Ultimately the cost surface cannot have values
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