PopulationCurve

Cargo featurefeatures = ["biology"]

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PopulationCurve draws population growth on axes of time against population, from 0 to years in duration seconds from delay, a dot at the head of each curve. Its model is one of three:

PopulationModel::Logistic: growth from n0 at rate r levels off at the dashed carrying capacity k. With compare the exponential curve with the same start and rate is drawn faded beside it, until it leaves the top.
PopulationModel::Exponential: the same growth with no limit.
PopulationModel::PredatorPrey: Lotka-Volterra, with prey and predators rising and falling in turn. PopulationModel::PREDATOR_PREY cycles about every six time units.

A legend names each curve in its colour from colors. series(count) gives the values the curves draw. Gallery scenes: PopulationCurve (logistic) and PredatorPrey.

PopulationCurve demo, first frame — `PopulationCurve` 7 s

PredatorPrey demo, first frame — `PredatorPrey` 7 s

use fframes_kit::prelude::*;

let logistic = PopulationCurve { k: 500.0, n0: 5.0, ..PopulationCurve::default() };
let n = &logistic.series(100)[0];
assert!((n[100] - 500.0).abs() < 5.0); // levelled off at K

fn cycles<'a>(ui: &mut Ui<'a, '_, '_>) -> Svgr<'a> {
    ui.show(PopulationCurve {
        model: PopulationModel::PREDATOR_PREY,
        years: 20.0,
        ..ui.defaults()
    })
}

API

Components are plain structs. Set the fields you need and fill the rest with ..ui.defaults(): the defaults below come from the current theme (theme. values are fields of Theme).

PopulationCurve

Field	Type	Default	Description
`model`	`PopulationModel`	`PopulationModel::Logistic`	Which curves: `Logistic`, `Exponential` or `PredatorPrey`.
`r`	`f64`	`0.8`	Growth rate per year (per unit of the time axis).
`k`	`f64`	`1000.0`	Carrying capacity, the population a logistic curve levels off at; it also sets the height of the vertical axis.
`n0`	`f64`	`10.0`	Starting population at time 0.
`years`	`f64`	`15.0`	Length of the time axis; the curves run from 0 to `years`.
`compare`	`bool`	`true`	Draws the faded exponential curve beside a logistic one when `true`.
`delay`	`f32`	`0.0`	Seconds after the container’s start before the curves begin to draw.
`duration`	`f32`	`5.0`	Seconds the curves take to draw from 0 to `years`.
`center`	`(f64, f64)`	`(-0.8, -0.3)`	The middle of the axes, in units of `ui.space`.
`x_length`	`f64`	`8.5`	Width of the axes, in units of `ui.space`.
`y_length`	`f64`	`5.2`	Height of the axes, in units of `ui.space`.
`colors`	`[Color; 2]`	`[Color::hex("#69db7c"), Color::hex("#ff8787")]`	Colours of the first and the second curve; a faded comparison curve uses the second.
`axis_color`	`Color`	`theme.colors.muted`	Colour of the axes.
`label_style`	`TextStyle`	`label_style`	The font of the axis labels, numbers and legend: family, size in pixels and weight.
`text_color`	`Color`	`theme.colors.text`	Colour of the legend and the carrying-capacity label.
`enter`	`Option<FadeIn>`	`None`	Fade in at the start; `None` for none.
`exit`	`Option<FadeOut>`	`None`	Fade out before the end; `None` for none.

Methods:

fn series(&self, count: usize) -> Vec<Vec<f64>>: The populations at count + 1 evenly spaced times from 0 to years: one series, or prey and then predators.

Feature biology · Source