[GRASS-user] r.mapcalculator and r.mapcalc

[Helmut Kudrnovsky]

>1 - Why wasn’t r.mapcalculator ported to grass7? It is great to use it from
within QGIS.

can't answer this one

>My r.mapcalc outputs int32 rasters (I want float32). Is there a way to
choose the output type?

from the manual [1]

------------------------
[...]
Functions
The functions currently supported are listed in the table below. The type of
the result is indicated in the last column. F means that the functions
always results in a floating point value, I means that the function gives an
integer result, and * indicates that the result is float if any of the
arguments to the function are floating point values and integer if all
arguments are integer. 

[...]
Floating point values in the expression
Floating point values in the expression are handled in a special way. With
arithmetic and logical operators, if either operand is float, the other is
converted to float and the result of the operation is float. This means, in
particular that division of integers results in a (truncated) integer, while
division of floats results in an accurate floating point value. With
functions of type * (see table above), the result is float if any argument
is float, integer otherwise.

Note: If you calculate with integer numbers, the resulting map will be
integer. If you want to get a float result, add the decimal point to integer
number(s).

If you want floating point division, at least one of the arguments has to be
a floating point value. Multiplying one of them by 1.0 will produce a
floating-point result, as will using float():

      r.mapcalc "ndvi = float(lsat.4 - lsat.3) / (lsat.4 + lsat.3)"
[...]
------------------------

HTH

[1] https://grass.osgeo.org/grass73/manuals/r.mapcalc.html



-----
best regards
Helmut
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