Convert between length and weight using the relationship
$$w = a l^b$$
where a and b are taken from the species parameter data frame.
l2w(l, params)w2l(w, params)
A vector with one entry for each species. l2w() returns a vector
of weights in grams and w2l() returns a vector of lengths in cm.
Lengths in cm. Either a single number or a vector with one number for each species.
A species parameter data frame or a MizerParams object.
Weights in grams. Either a single number or a vector with one number for each species.
This is useful for converting a length-based species parameter to a weight-based species parameter.
If any a or b parameters are missing the default values a = 0.01 and
b = 3 are used for the missing values.