add_total_line: Add a total line to plotting data by summing over its series

In mizer: Dynamic Multi-Species Size Spectrum Modelling

Add a total line to plotting data by summing over its series

Description

The total has to be formed after the size coordinate has been converted, not before. On a weight axis every series shares the model's weight grid, so summing at equal weight and summing at equal position are the same thing. On a length axis they are not: each species, and the resource, converts weight to length with its own allometric relationship, so at a given length the series sit at different weights and their grids no longer coincide. The sum that means something there is the sum at equal length — the number of organisms per unit length, whatever they are — which is what this computes.

Usage

add_total_line(
  plot_dat,
  x_var = names(plot_dat)[[1]],
  value_col = 2,
  by = NULL
)

Arguments

plot_dat	A data frame of plotting data with a size column, a value column and a Species column.
x_var	Name of the size column. Defaults to the first column.
value_col	Name or index of the value column. Defaults to the second.
by	Names of further columns identifying separate plots, such as the time of an animation frame or the model of a comparison. A total is formed within each of their combinations.

Details

Each series is interpolated onto the sorted union of all the size coordinates, linearly in the logarithm of size, since the grid is logarithmic. A series contributes nothing outside its own range. When the series already share a grid — always on a weight axis, and on a length axis whenever the weight-length parameters agree — the union is that grid and the interpolation reproduces the values exactly, so nothing is approximated in the cases where nothing needs to be.

Value

plot_dat with the total appended as a series named "Total".

mizer documentation built on Aug. 24, 2026, 9:08 a.m.