uom Units of Measurement

The 'units' attribute of FLQuant objects provides a mechanism for keeping track of the units of measurement of that particular piece of data.

Usage

uom(op, u1, u2)

uomUnits(unit = missing)

Arguments

op: The arithmetic operator to be used, one of '+', '-', '*' or '/'
u1: The units of measurement string of the first object
u2: The units of measurement string of the second object
unit: A character vector for one or more units to be compared with those known to uom.

Value

uom returns a string with the corresponding units of measurement, or a character vector, showing the operation carried out, when units are not known to uom or not compatible, e.g. "100 * d".

uomUnits returns TRUE or FALSE if unit is given, otherwise a character vector with all units known to uom.

Details

Arithmetic operators for 'FLQuant' objects are aware of a limited set of units of measurement and will output the right unit when two object are arithmetically combined. For example, the product of object with units of 'kg' and '1000' will output an object with 'units' of 't' (for metric tonnes).

Operations involving combinations of units not defined will issue a warning, and the resulting 'units' attribute will simply keep a string indicating the input units of measurement and the operation carried out, as in '10 * 1000'.

Note that no scaling or modification of the values in the object takes place.

Conversion across units is carried out by the uom() function

The list of units known to uom is stored internally but can be queried by calling uomUnits() with no arguments. If a character vector is provided, a logical is returned telling whether the string is included or not in that table.

Author

The FLR Team

Examples


# Conversion between weights
FLQuant(1, units='kg') * FLQuant(1000, units='1')
#> An x of class "FLQuant"
#> , , unit = unique, season = all, area = unique
#> 
#>      year
#> quant 1   
#>   all 1000
#> 
#> units:  kg 

# Conversion between mortalities
FLQuant(0.2, units='m') + FLQuant(0.34, units='f')
#> An x of class "FLQuant"
#> , , unit = unique, season = all, area = unique
#> 
#>      year
#> quant 1   
#>   all 0.54
#> 
#> units:  z 

# Check if units are known
uomUnits('kg')
#> [1] TRUE
uomUnits('kell')
#> [1] FALSE