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In QGIS - I have an irregularly shaped raster - I wish to clip an irregular area out of it (call it raster A) with that area set to null.

I masked the area (vector polygon) I want to remove and used warp > reproject to create the second raster (lets call it B) that effectively contains the portion of raster A I want to set to null.

I intended to use raster calculator to subtract raster B from raster A which would leave the areas to be removed with value 0, and I could then reproject this setting 0 to null - however this doesnt work as outside the masked area 'A - null = null' and I end up with a calculated raster of 0 in only the area I want to remove, and null everywhere else.

How can I treat the areas on raster B that are null as zero in the calculation? Alternatively, is there any less convoluted way I can complete this process?

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Use nan_to_num to replace nans with zeroes. In the calculator, it will look like this:

nan_to_num(A@1) + nan_to_num(B@1)

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