Functions for drawing selected slice view.

R/slice.R

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+#' This function generates an axis-parallel slice display
+#'
+#' more info on the function
+#'
+#' @param data data frame containing only variables used for the display
+#' @param h slice thickness
+#' @param v1 column number of variable mapped to x-axis
+#' @param v2 column number of variable mapped to y-axis
+#' @param center center point vector used for anchoring the slice,
+#'    if NULL the mean of the data is used
+#' @param col grouping vector mapped to color in the display
+#'
+#' @return ggplot object showing the sliced data
+#' @export
+#' @examples
+#' d <- geozoo::sphere.hollow(4, 1000)$points
+#' ggslice(d, 0.3, 1, 2)
+#' ggslice(d, 0.3, 1, 2, center = c(0, 0, 0.7, 0))
+
+
+ggslice <- function(data, h, v1=1, v2=2, center=NULL,
+										col=NULL) {
+	plane <- basis_proj(v1, v2, ncol(data))
+	ggslice_projection(data, h, plane, center, col)
+}
+
+ggslice_projection <- function(data, h, proj, center=NULL,
+															col=NULL) {
+	d <- tourr::anchored_orthogonal_distance(proj, data, anchor = center)
+	data_proj <- as.matrix(data) %*% proj
+	colnames(data_proj) <- c("P1", "P2")
+	data_proj <- tibble::as.tibble(data_proj)
+	ggplot2::ggplot(data_proj[d >= h,], aes(P1, P2)) +
+		geom_point(aes(color = col[d >= h]), pch = 46, alpha = 0.5) +
+		geom_point(data = data_proj[d < h,],
+							 mapping = aes(color = col[d < h])) +
+		theme_bw() +
+		coord_fixed()
+}
+
+basis_vector <- function(i, p){
+	v <- rep(0, p)
+	v[i] <- 1
+	v
+}
+basis_proj <- function(i, j, p){
+	matrix(c(basisVector(i, p), basisVector(j, p)), ncol=2)
+}