The quantity plotted by plotSpectra() is the number density multiplied by
w^power. That power is the sum of two independent choices: whether the
quantity is a biomass density (a factor of w) or a number density, and
whether it is a density with respect to logarithmic size (another factor of
w) or with respect to size. The two choices are what determine the y-axis
label and the Jacobian used when converting to a length axis, and they are
not recoverable from power alone: power = 1 is both the biomass density
with respect to weight and the number density with respect to logarithmic
weight.
resolve_spectrum_power(power = NULL, biomass = NULL, per_log_size = NULL)A list with entries power, biomass and per_log_size.
The power of weight multiplying the number density, or NULL.
Whether to plot a biomass density rather than a number
density, or NULL. The default is TRUE.
Whether to plot a density with respect to logarithmic
size rather than with respect to size, or NULL. The default is FALSE.
Users therefore express the choice with the biomass and per_log_size
flags. The power argument remains available, both for backwards
compatibility and as an escape hatch for powers that are not the sum of two
flags. Each argument is NULL when it was not supplied by the user.