[GRASS-dev] [GRASS GIS] #2053: r.recode: 0.0 or 1.0 as limits do not seem to be taken into account

[GRASS GIS]

#2053: r.recode: 0.0 or 1.0 as limits do not seem to be taken into account
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 Reporter:  nikosa                                  |       Owner:  grass-dev@…              
     Type:  defect                                  |      Status:  new                      
 Priority:  major                                   |   Milestone:  7.0.0                    
Component:  Raster                                  |     Version:  unspecified              
 Keywords:  r.recode, DCELL, CELL, rules, needinfo  |    Platform:  Unspecified              
      Cpu:  Unspecified                             |  
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Comment(by glynn):

 Replying to [comment:5 glynn]:

 > I wouldn't suggest using the input map's type for the input type unless
 this will produce identical results.

 From examining lib/raster/fpreclass.c, it appears that they will produce
 identical results (int and float values are simply converted to double),
 so this is a non-issue.


 However, this might be a good time to re-examine how floating-point values
 are converted to integers both in fpreclass.c and put_row.c.

 Both cases simply use a C cast, which is defined as discarding the
 fractional part, i.e. rounding toward zero (inwards). The GRASS
 quantisation functions are only used when reading floating-point maps as
 integer, not when writing.

 This is one of the least useful rounding modes, due to its anti-symmetric
 behaviour (i.e. positive numbers are rounded down, negative numbers are
 rounded up). Rounding to nearest integer or rounding toward negative
 infinity (i.e. floor()) are usually preferred.

 Another issue with a C cast is that if the result is outside the range of
 an integer, the behaviour is undefined. Ideally such values should be
 either converted to null or clamped to the most positive/negative
 representable value.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/2053#comment:8>
GRASS GIS <http://grass.osgeo.org>