---
title: "Quickstart"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Quickstart}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  fig.width = 7,
  fig.height = 4
)
```

# Quickstart

This vignette illustrates the basic use of `demovuln`.

```{r}
library(demovuln)
```

We define a simple two-stage projection matrix. Columns are source stages at time `t`, and rows are destination stages at time `t + 1`.

```{r}
A <- matrix(
  c(0.0, 0.4,
    2.0, 0.7),
  nrow = 2,
  byrow = FALSE
)

A
```

```{r}
model <- matrix_population_model(
  A,
  adult_stages = 2,
  juvenile_stages = 1
)
```

We simulate a perturbation affecting adult survival.

```{r}
sim <- simulate_dynamics(
  model,
  target = "adult_survival",
  magnitude = 0.25,
  duration = 1,
  period = 3,
  t_max = 50,
  recovery_steps = 10
)

sim$reduction
```

```{r}
plot(
  sim$baseline_abundance,
  type = "l",
  lwd = 2,
  xlab = "Time step",
  ylab = "Relative population size",
  ylim = range(c(sim$baseline_abundance, sim$abundance))
)

lines(sim$abundance, lwd = 2, lty = 2)

legend(
  "topright",
  legend = c("Baseline", "Perturbed"),
  lty = c(1, 2),
  lwd = 2,
  bty = "n"
)
```