units (version 0.8-5)

Math.units: Mathematical operations for units objects

Description

Mathematical operations for units objects

Usage

# S3 method for units
Math(x, ...)

Arguments

x

object of class units

...

parameters passed on to the Math functions

Details

Logarithms receive a special treatment by the underlying udunits2 library. If a natural logarithm is applied to some unit, the result is ln(re 1 unit), which means natural logarithm referenced to 1 unit. For base 2 and base 10 logarithms, the output lb(...) and lg(...) respectively instead of ln(...).

This is particularly important for some units that are typically expressed in a logarithmic scale (i.e., bels, or, more commonly, decibels), such as Watts or Volts. For some of these units, the default udunits2 database contains aliases: e.g., BW (bel-Watts) is an alias of lg(re 1 W); Bm (bel-milliWatts) is an alias of lg(re 0.001 W); BV is an alias of lg(re 1 V) (bel-Volts), and so on and so forth (see the output of valid_udunits() for further reference).

Additionally, the units package defines B, the bel, by default (because it is not defined by udunits2) as an alias of lg(re 1), unless a user-provided XML database already contains a definition of B, or the define_bel option is set to FALSE (see help(units_options)).

Examples

# roundings, cummulative functions
x <- set_units(sqrt(1:10), m/s)
signif(x, 2)
cumsum(x)

# trigonometry
sin(x) # not meaningful
x <- set_units(sqrt(1:10), rad)
sin(x)
cos(x)
x <- set_units(seq(0, 1, 0.1), 1)
asin(x)
acos(x)

# logarithms
x <- set_units(sqrt(1:10), W)
log(x) # base exp(1)
log(x, base = 3)
log2(x)
log10(x)
set_units(x, dBW) # decibel-watts
set_units(x, dBm) # decibel-milliwatts