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[Feat] Add JSON output to r.describe #4903

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NishantBansal2003 opened this issue Jan 1, 2025 · 5 comments · May be fixed by #4918
Open

[Feat] Add JSON output to r.describe #4903

NishantBansal2003 opened this issue Jan 1, 2025 · 5 comments · May be fixed by #4918
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enhancement New feature or request

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@NishantBansal2003
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Add JSON output for easy parsing of r.describe output.

Describe the solution you'd like
Add an option for format, such as format=plain for the current output format and format=json for the JSON output.

A possible JSON layout could be:

[
  {
    "values": "0.996534-8.677654"
  },
  {
    "values": "8.677654-16.358774"
  },
  {
    "values": "16.358774-24.040000"
  }
]

Describe alternatives you've considered
Alternatively(helpful for numerical operations or parsing), the JSON layout could look like this:

[
  {
    "min": "0.996534",
    "max": "8.677654"
  },
  {
    "min": "8.677654",
    "max": "16.358774"
  },
  {
    "min": "16.358774",
    "max": "24.040000"
  }
]
@NishantBansal2003 NishantBansal2003 added the enhancement New feature or request label Jan 1, 2025
@NishantBansal2003
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Hey @echoix, I was trying to write tests for the above change, and I am using this raster map:

map = if(row() == 5 && col() == 5, null(), if(row() % 2 == 0, col() * 0.5, -col() * 0.5))

When I run the following command:

r.describe -1 map

I get the following output:

*
-5.000000--4.960784
-4.529412--4.490196
-4.019608--3.980392
-3.509804--3.470588
-3.039216--3.000000
-2.529412--2.490196
-2.019608--1.980392
-1.549020--1.509804
-1.039216--1.000000
-0.529412--0.490196
0.450980-0.490196
0.960784-1.000000
1.470588-1.509804
1.941176-1.980392
2.450980-2.490196
2.960784-3.000000
3.431373-3.470588
3.941176-3.980392
4.450980-4.490196
4.960784-5.000000

Is this output format correct(for negative values)? Also, when should we use the "-" symbol and "thru" in the r.describe output?

@NishantBansal2003 NishantBansal2003 linked a pull request Jan 5, 2025 that will close this issue
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@echoix
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echoix commented Jan 5, 2025

Can another "expert" or someone knowing r.describe jump in? I don't know what to answer here

@neteler
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neteler commented Jan 5, 2025

The thru of r.describe is understood by e.g. r.reclass and other commands. Hence, it is the official syntax (yes, looks oldish but works since ~1984).

The output of r.describe is also (to remain) machine readable:

ag --python r.describe
scripts/d.rast.leg/d.rast.leg.py
123:    cats = gs.read_command("r.describe", map=map, flags="1n")

scripts/r.grow/testsuite/test_r_grow.py
61:        shrined_range = SimpleModule("r.describe", flags="i", _map=self.mapShrunkNoNULL)

gui/wxpython/rdigit/controller.py
466:                        "r.describe", flags="1n", map=name, quiet=True

Of course, with increasing JSON support we get modern options here.

@petrasovaa
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Sorry coming late to this, but I would like to suggest alternative schema. The JSON output should have the raw numbers. Unfortunately the r.describe output is pretty complex and depends on CELL/FCELL, so this suggestion tries to capture it:

Integer maps current behavior:

r.describe my_int_map 
* 1-3 10-12 15

r.describe my_int_map -r
1 thru 15
*

r.describe my_int_map -1
*
1
2
3
10
11
12
15

With json:

r.describe my_int_map format=json
{"ranges": [{"min": 1, "max": 3}, {"min": 10, "max": 12}, {"min": 15, "max": 15}],
"has_nulls": true}

r.describe my_int_map -r format=json
{"min": 1, "max": 15, "has_nulls": true}

r.describe my_int_map -1 format=json
{"values": [1,2,3,4,5,10,11,12,15],
"has_nulls": true}

Floating point maps current behavior:

r.describe elevation
55.578793-156.329865

r.describe elevation -r
55.578793-156.329865

r.describe elevation -1 nsteps=3
55.578793-89.162483
89.162483-122.746174
122.746174-156.329865

With json:

r.describe elevation format=json
{"ranges": [{"min": 55.578793, "max": 156.329865}],
"has_nulls": false}

r.describe elevation format=json -r
{"min": 55.578793, "max": 156.329865, "has_nulls": false}

r.describe elevation -1 nsteps=3 format=json
{"ranges": [{"min": 55.578793, "max": 89.162483}, {"min": 89.162483, "max": 122.746174}, {"min": 122.746174, "max": 156.329865}],
"has_nulls": false}

@nilason nilason moved this to In Progress in GRASS JSON Outputs Jan 15, 2025
@NishantBansal2003
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Hey @petrasovaa, should we ignore the 'nv' option for null value strings in JSON?
I suggest using something like "null_value": "*". wdyt?

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enhancement New feature or request
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r.describe: Add JSON support NishantBansal2003/grass
4 participants
@neteler @petrasovaa @echoix @NishantBansal2003