Missing values

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Missing values#

For indices calculation, CLIX uses built-in functions from xclim for the handling of missing values in input data. Output values are properly masked in case input values are missing or invalid. With the option --check_missing the following missing value methods are available:

  • wmo: A result is missing if 11 days are missing, or 5 consecutive values are missing in a month. Default.

  • pct: A result is missing if more than a given fraction of values are missing.

  • any: A result is missing if any input value is missing.

  • at_least_n: A result is missing if less than a given number of valid values are present.

  • skip: Skip missing value detection.

Missing options#

For the method pct the maximum tolerated proportion of missing values per output frequency must be defined by the addtional option --allowed_miss_pct, given as a float between 0 and 1.

For the method at_least_n masks output frequencies as missing if they don’t have at least a given number of valid values. The additional option --min_valid_values must be given with an integer. It specifies the minimum number of needed valid values.

CLIX uses the wmo method by default if --check_missing is not set.

Example: Skip missing value detection when calculating summer days

This command calculates yearly txge25 (summer days) and ignores any missing values:

clixrun --input /path/to/tasmax_with_nas.nc --check_missing skip --frequency year txge25

This will give results even if there are (a lot of) missing values.

Example: Use the pct method for calculating summer days

This command calculates monthly txge25 (summer days) only if no more than a fraction of --allowed_miss_pct are missing per input time series (grid cell) for each timestep of the output frequency:

clixrun --input /path/to/tasmax_with_nas.nc --frequency month --check_missing pct --allowed_miss_pct 0.08 txge25

Example: Use the at_least_n method for calculating summer days

This command calculates monthly txge25 (summer days) only if at least --min_valid_values valid values are available in the input time series (grid cell) for each timestep of the output frequency:

clixrun --input /path/to/tasmax_with_nas.nc --frequency month --check_missing at_least_n --min_valid_values 20 txge25

Example: Use the any method for calculating summer days

This command calculates yearly txge25 only if all input values are valid values. As soon as any of the input values is missing value, the result is a missing value:

clixrun --input /path/to/tasmax_with_nas.nc --frequency year --check_missing any txge25
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