[R] allequal diff

[Ben Bolker]

   Digging into the code for raster::compareRaster():

library(raster)
r <- raster(ncol=3, nrow=3)
values(r) <- 1:ncell(r)
r2 <- r
values(r2) <- c(1:8,10)
all.equal(getValues(r), getValues(r2), tolerance = 0)
[1] "Mean relative difference: 0.1111111"

    compareRaster has fancier machinery internally for doing the 
comparison for large rasters a block at a time if everything can't fit 
in memory at the same time ...




On 2024-08-15 9:14 a.m., SIBYLLE STÖCKLI via R-help wrote:
> Dear community
> 
> 
> 
> Similar to the example of the rdocumentation, my idea is to use all.equal
> and to print the difference.
> 
> https://www.rdocumentation.org/packages/base/versions/3.6.2/topics/all.equal
> 
> 
> 
>> d45 <- pi*(1/4 + 1:10)
> 
>> stopifnot(
> 
> +     all.equal(tan(d45), rep(1, 10)))          # TRUE, but
> 
>> all      (tan(d45) == rep(1, 10))         # FALSE, since not exactly
> 
> [1] FALSE
> 
>> all.equal(tan(d45), rep(1, 10), tolerance = 0)  # to see difference
> 
> [1] "Mean relative difference: 1.29526e-15"
> 
>>
> 
> 
> 
> Unfortunately, I just get "FALSE" not the difference.
> 
>> r2_resampled <- resample(r2, r1)
> 
>> compareRaster(r1, r2_resampled)
> 
> [1] TRUE
> 
>> # Compare rasters
> 
>> result <- all.equal(r1, r2_resampled)
> 
> Warning message:
> 
> In compareRaster(target, current, ..., values = values, stopiffalse =
> stopiffalse,  :
> 
>    not all objects have the same values
> 
>> print(result)
> 
> [1] FALSE
> 
>>
> 
> 
> 
> Kind regards
> 
> Sibylle
> 
> 
> 	[[alternative HTML version deleted]]
> 
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-- 
Dr. Benjamin Bolker
Professor, Mathematics & Statistics and Biology, McMaster University
Director, School of Computational Science and Engineering
 > E-mail is sent at my convenience; I don't expect replies outside of 
working hours.