| Math.units {units} | R Documentation |
Mathematical operations for units objects
## S3 method for class 'units' Math(x, ...)
x |
object of class units |
... |
parameters passed on to the Math functions |
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)).
# 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