---
title: "Discretized Curves and Grouped Stability Selection"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Discretized Curves and Grouped Stability Selection}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
has_grpreg <- requireNamespace("grpreg", quietly = TRUE)
```

`SelectBoost.FDA` can now go from raw discretized curves to stability summaries
without any manual matrix construction. The design object stores the fitted
preprocessing, the flattened matrix used by the selector, and the reversible
map back to the original curve domain.

## Build a functional design

```{r}
library(SelectBoost.FDA)
data("spectra_example", package = "SelectBoost.FDA")

signal <- fda_grid(
  spectra_example$predictors$signal,
  argvals = spectra_example$grid,
  name = "signal",
  unit = "nm"
)
nuisance <- fda_grid(
  spectra_example$predictors$nuisance,
  argvals = spectra_example$grid,
  name = "nuisance",
  unit = "nm"
)

design <- fda_design(
  response = spectra_example$response,
  predictors = list(signal = signal, nuisance = nuisance),
  scalar_covariates = spectra_example$scalar_covariates,
  scalar_transform = fda_standardize(),
  family = "gaussian"
)

design
summary(design)
head(selection_map(design))
```

The design stores the fitted preprocessing object as well. In this first
workflow the functional predictors stay on their original grid, while the
scalar covariates are standardized.

```{r}
design$preprocessor
summary(design$preprocessor)
```

## Fit grouped stability selection

The following chunk is evaluated only when `grpreg` is installed.

```{r, eval = has_grpreg}
fit <- fit_stability(
  design,
  selector = "grpreg",
  B = 30,
  sample_fraction = 0.5,
  cutoff = 0.7,
  seed = 1
)

fit
summary(fit)
head(selection_map(fit))
plot(fit, type = "group")
selected(fit, level = "group")
```

## Interval-level summaries

You can also move from predictor-level groups to non-overlapping intervals.

```{r, eval = has_grpreg}
interval_fit <- interval_stability_selection(
  design,
  width = 5,
  selector = "grpreg",
  B = 20,
  cutoff = 0.6,
  seed = 2
)

head(interval_fit$interval_table)
plot(
  interval_fit,
  type = "interval",
  value = "mean",
  facet = "predictor",
  legend_title = "Mean frequency",
  palette = grDevices::heat.colors(24)
)
selected(interval_fit, level = "group")
```