## ----setup, include=FALSE-----------------------------------------------------
knitr::opts_chunk$set(collapse = TRUE, comment = "#>")

if (!requireNamespace("bigmemory", quietly = TRUE)) {
  cat("This vignette requires the 'bigmemory' package.\n")
  knitr::knit_exit()
}

library(bigKNN)
library(bigmemory)

## ----helpers, include=FALSE---------------------------------------------------
clean_graph <- function(x) {
  out <- as.data.frame(x)
  rownames(out) <- NULL
  out[order(out$from, out$to), , drop = FALSE]
}

## ----create-reference---------------------------------------------------------
reference_points <- data.frame(
  id = paste0("p", 1:6),
  x1 = c(0.0, 0.3, 1.2, 4.0, 4.3, 5.2),
  x2 = c(0.0, 0.0, 0.0, 4.0, 4.1, 4.0)
)

reference <- as.big.matrix(as.matrix(reference_points[c("x1", "x2")]))

reference_points

## ----directed-knn-graph-------------------------------------------------------
directed_knn <- knn_graph_bigmatrix(
  reference,
  k = 1,
  format = "edge_list",
  symmetrize = "none"
)

clean_graph(directed_knn)

## ----mutual-graph-------------------------------------------------------------
mutual_knn <- mutual_knn_graph_bigmatrix(
  reference,
  k = 1,
  format = "edge_list"
)

clean_graph(mutual_knn)

## ----mutual-wrapper-----------------------------------------------------------
identical(
  clean_graph(mutual_knn),
  clean_graph(knn_graph_bigmatrix(reference, k = 1, format = "edge_list", symmetrize = "mutual"))
)

## ----snn-graph----------------------------------------------------------------
snn_count <- snn_graph_bigmatrix(
  reference,
  k = 2,
  weight = "count",
  format = "edge_list"
)

snn_jaccard <- snn_graph_bigmatrix(
  reference,
  k = 2,
  weight = "jaccard",
  format = "edge_list"
)

merge(
  clean_graph(snn_count),
  clean_graph(snn_jaccard),
  by = c("from", "to"),
  suffixes = c("_count", "_jaccard")
)

## ----radius-graph-------------------------------------------------------------
radius_directed <- radius_graph_bigmatrix(
  reference,
  radius = 1.1,
  format = "edge_list",
  symmetrize = "none"
)

radius_union <- radius_graph_bigmatrix(
  reference,
  radius = 1.1,
  format = "edge_list",
  symmetrize = "union"
)

clean_graph(radius_directed)
clean_graph(radius_union)

## ----radius-symmetry----------------------------------------------------------
identical(
  clean_graph(radius_graph_bigmatrix(reference, radius = 1.1, format = "edge_list", symmetrize = "union")),
  clean_graph(radius_graph_bigmatrix(reference, radius = 1.1, format = "edge_list", symmetrize = "mutual"))
)

## ----symmetrize-comparison----------------------------------------------------
graph_none <- knn_graph_bigmatrix(reference, k = 1, format = "edge_list", symmetrize = "none")
graph_union <- knn_graph_bigmatrix(reference, k = 1, format = "edge_list", symmetrize = "union")
graph_mutual <- knn_graph_bigmatrix(reference, k = 1, format = "edge_list", symmetrize = "mutual")

data.frame(
  symmetrize = c("none", "union", "mutual"),
  n_edges = c(nrow(clean_graph(graph_none)), nrow(clean_graph(graph_union)), nrow(clean_graph(graph_mutual))),
  row.names = NULL
)

## ----graph-coercion-----------------------------------------------------------
triplet_graph <- as_triplet(graph_mutual)
sparse_graph <- as_sparse_matrix(
  knn_graph_bigmatrix(
    reference,
    k = 1,
    format = "edge_list",
    symmetrize = "union",
    include_distance = FALSE
  )
)

triplet_graph
class(sparse_graph)
Matrix::summary(sparse_graph)

## ----graph-roundtrip----------------------------------------------------------
clean_graph(as_edge_list(sparse_graph))

## ----downstream-usage---------------------------------------------------------
degree <- Matrix::rowSums(sparse_graph)

data.frame(
  vertex = reference_points$id,
  degree = as.numeric(degree),
  row.names = NULL
)