r.recode results in integer when floating numbers are expected [Bug] about grass

[dhdeangelis]

You need to add the -d flag to your command to achieve your expected results:

-d Force output to 'double' raster map type (DCELL)

Try:

echo "0.0:18.7:0.0:1.0" | r.recode -d input=myinput output=myoutput rules=-

[ecodiv]

You need to add the -d flag to your command to achieve your expected results:

-d Force output to 'double' raster map type (DCELL)

Try:

echo "0.0:18.7:0.0:1.0" | r.recode -d input=myinput output=myoutput rules=-

Thanks. I know you can use the -d flag (and I wrote that in the bug report), but the point I was trying to make is that based on the manual, I would not necessarily expect r.recode to convert the floating map to an integer map, as I used decimal numbers for the new minimum and maximum value. I think that either the behavior should be changed, or the behavior (when does the function change the data type) should be explained more explicitly.

[dhdeangelis]

I know you can use the -d flag (and I wrote that in the bug report)

I see, I missed that.

based on the manual, I would not necessarily expect r.recode to convert the floating map to an integer map, as I used decimal numbers for the new minimum and maximum value. I think that either the behavior should be changed, or the behavior (when does the function change the data type) should be explained more explicitly.

I agree with this. I also find the manual confusing on this regard. The manual first states that r.recode is for recoding categorical maps, which it seems to be made for, but then gives an example of rescaling, for which r.mapcalc is more convenient.

[ninsbl]

This seems like a bug to me.

r.recode appears to be intended to produce FCELL results too. See e.g.: https://github.com/OSGeo/grass/blob/25961a86c26765f293d582900b00bb37403a780d/raster/r.recode/read_rules.c#L143C25-L143C29

[dhdeangelis]

It seems that the problem lies in parsing or managing the input, as numbers ending in zero are not interpreted as float.

Example:
echo "0.0:18.7:0.0:1.0" | r.recode input=r output=test rules=- --overwrite
produces a raster of type CELL
while
echo "0.0:18.7:0.01:1.0" | r.recode input=r output=test rules=- --overwrite
or
echo "0.0:18.7:0.0:1.01" | r.recode input=r output=test rules=- --overwrite
produce rasters of type FCELL

Edit: deleted reference to rules, as I could not trace the exact source of the problem.

[dhdeangelis]

It seems to me that this part in read_rules.c is not working as intended:

grass/raster/r.recode/read_rules.c

Lines 136 to 146 in f4d8c62

	int update_type(RASTER_MAP_TYPE *map_type, DCELL val)
	{
	/* check if val is not an integer number */
	if (make_dcell)
	*map_type = DCELL_TYPE;
	else {
	if ((DCELL)((CELL)val) != val)
	*map_type = FCELL_TYPE;
	}
	return 0;
	}

Perhaps line 142 could be replaced with a call to a function to tell if val is a float or integer. . I am not so fluent in C but it seems that is not so straightforward.

A simple work around could be to default output to integer, unless it is forced to double using the -d switch, or to float using a new switch, for example: -f. This I just tested and works. But it is perhaps not the expected behaviour? Also it adds a new switch and may break backwards compatibility.