flag_masks formatting for larger bit depth
mps01060 opened this issue · 1 comments
mps01060 commented
For our project we have ~20 independent flag_masks that can simultaneously be triggered (QA/QC flags). The current implementation of "flag_masks" works well with operations such as "==" and "isin" for integers larger than 8-bit:
import xarray as xr
import numpy as np
import cf_xarray
# Create example 32-bit flag_masks
flag_indep_uint32 = xr.DataArray(
2**np.arange(32, dtype=np.uint32),
dims=("time",),
attrs={
"flag_masks": [2**i for i in range(32)],
"flag_meanings": " ".join([f"flag_{i}" for i in range(32)]),
"standard_name": "flag_independent",
},
name="flag_var",
)Find where flag_0 is True
flag_indep_uint32.cf == "flag_0"<xarray.DataArray 'flag_var' (time: 32)>
array([ True, False, False, False, False, False, False, False, False,
False, False, False, False, False, False, False, False, False,
False, False, False, False, False, False, False, False, False,
False, False, False, False, False])
Dimensions without coordinates: time
Find where flag_0 or flag_1 or flag_31 are True
flag_indep_uint32.cf.isin(["flag_0", "flag_1", "flag_31"])<xarray.DataArray 'flag_var' (time: 32)>
array([ True, True, False, False, False, False, False, False, False,
False, False, False, False, False, False, False, False, False,
False, False, False, False, False, False, False, False, False,
False, False, False, False, True])
Dimensions without coordinates: time
The one part that doesn't seem supported is just using the ".cf" to print the flags/bits:
flag_indep_uint32.cfTraceback (most recent call last):
File "<stdin>", line 1, in <module>
File ".../python3.10/site-packages/cf_xarray/accessor.py", line 1543, in __repr__
return ("".join(self._generate_repr(rich=False))).rstrip()
File ".../lib/python3.10/site-packages/cf_xarray/accessor.py", line 1561, in _generate_repr
_format_flags(self, rich), title="Flag Variable", rich=rich
File ".../lib/python3.10/site-packages/cf_xarray/formatting.py", line 200, in _format_flags
bitstring[abs(b)] = _format_cf_name("1" if b >= 0 else "0", rich)
IndexError: list assignment index out of range
The _format_flags and find_set_bits have some uint8-dependent code. Internally, we made some small changes here:
https://github.com/mps01060/cf-xarray/tree/morebits
This hasn't been thoroughly tested and there is probably a much more concise way of adding this support compared to what I have. For the same uint32 example earlier, the updated code displays as
flag_indep_uint32.cfFlag Variable:
Flag Meanings: flag_0: 1 / Bit: ...............................1
flag_1: 2 / Bit: ..............................1.
flag_2: 4 / Bit: .............................1..
flag_3: 8 / Bit: ............................1...
flag_4: 16 / Bit: ...........................1....
flag_5: 32 / Bit: ..........................1.....
flag_6: 64 / Bit: .........................1......
flag_7: 128 / Bit: ........................1.......
flag_8: 256 / Bit: .......................1........
flag_9: 512 / Bit: ......................1.........
flag_10: 1024 / Bit: .....................1..........
flag_11: 2048 / Bit: ....................1...........
flag_12: 4096 / Bit: ...................1............
flag_13: 8192 / Bit: ..................1.............
flag_14: 16384 / Bit: .................1..............
flag_15: 32768 / Bit: ................1...............
flag_16: 65536 / Bit: ...............1................
flag_17: 131072 / Bit: ..............1.................
flag_18: 262144 / Bit: .............1..................
flag_19: 524288 / Bit: ............1...................
flag_20: 1048576 / Bit: ...........1....................
flag_21: 2097152 / Bit: ..........1.....................
flag_22: 4194304 / Bit: .........1......................
flag_23: 8388608 / Bit: ........1.......................
flag_24: 16777216 / Bit: .......1........................
flag_25: 33554432 / Bit: ......1.........................
flag_26: 67108864 / Bit: .....1..........................
flag_27: 134217728 / Bit: ....1...........................
flag_28: 268435456 / Bit: ...1............................
flag_29: 536870912 / Bit: ..1.............................
flag_30: 1073741824 / Bit: .1..............................
flag_31: 2147483648 / Bit: 1...............................
Coordinates:
CF Axes: X, Y, Z, T: n/a
CF Coordinates: longitude, latitude, vertical, time: n/a
Cell Measures: area, volume: n/a
Standard Names: n/a
Bounds: n/a
Grid Mappings: n/a
Thank you for any help / suggestions!
dcherian commented
very nice. I will happily merge this improvement. Can you send in a PR with a test please?