[R] allequal diff

[Ben Bolker]

   To do this, I think you'll have to compare the extent (using the 
extent() function) and/or number of rows and columns and/or resolution 
of the two rasters. (Print the source code of compareRasters() and dig 
through it to see what's being compared ...)

On 8/18/24 14:00, SIBYLLE STÖCKLI via R-help wrote:
> Dear Ivan
>
> Thanks a lot for this very nice example.
>
> Is it true that all.equal just compares y values?
> Based on this help here I think so and the value I got is the difference for the y-values.
> https://www.statology.org/all-equal-function-r/
>
> However, here I see x and y testing?
> https://www.rdocumentation.org/packages/base/versions/3.6.2/topics/all.equal
> I am actually interested in the x values (x-y coordinates). Test if x-y coordinates of both 25-m-pixel rasters are the same. Ther may be a small shift or differences in the number of decimal places.
>
> Kind regards
> Sibylle
>
>
>
> -----Original Message-----
> From: Ivan Krylov <ikrylov using disroot.org>
> Sent: Friday, August 16, 2024 11:45 AM
> To: sibylle.stoeckli using gmx.ch
> Cc: 'SIBYLLE STÖCKLI via R-help' <r-help using r-project.org>
> Subject: Re: [R] allequal diff
>
> В Fri, 16 Aug 2024 11:32:58 +0200
> <sibylle.stoeckli using gmx.ch> пишет:
>
>> # values and mask r1
>> r1 <- getValues(r1)
>> mask1 <- is.na(r1)
>> # Do the same for r2
>> r2 <- getValues(r2_resampled)
>> mask2 <- is.na(r2)
>>
>> # Combine the masks
>> all.equal(r1[!(mask1 & mask2)], r2[!(mask1 & mask2)])
> Let's consider a more tangible example:
>
> # The vectors `x` and `y` start out equal x <- y <- 1:10 # But then their different elements are made missing x[c(1,3,4)] <- NA y[c(3,8)] <- NA
>
> Now, `is.na(x) & is.na(y)` gives the third element as the only element missing in both x and y:
>
> mask1 <- is.na(x)
> mask2 <- is.na(y)
> all.equal( # not the comparison you are looking for
>   x[!(mask1 & mask2)], # still two more elements missing
>   y[!(mask1 & mask2)]  # still one more element missing
> )
>
> If you want to ignore all missing elements, you should combine the masks using the element-wise "or" operation ("missing in x and/or y"), not the element-wise "and" operation ("missing in both x and y at the same time"):
>
> mask1 & mask2 # drops element 3
> # [1] FALSE FALSE  TRUE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
> mask1 | mask2 # drops elements 1, 3, 4, 8 # [1]  TRUE FALSE  TRUE  TRUE FALSE FALSE FALSE  TRUE FALSE FALSE
>
> --
> Best regards,
> Ivan
>
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