feat: add plot(vertex.label.angle = , vertex.label.adj = ) arguments to rotate vertex labels

R/plot.R

@@ -112,6 +112,8 @@ plot.igraph <- function(
   label.degree <- params("vertex", "label.degree")
   label.color <- params("vertex", "label.color")
   label.dist <- params("vertex", "label.dist")
+  label.angle <- params("vertex", "label.angle")
+  label.adj <- params("vertex", "label.adj")
   labels <- params("vertex", "label")
   shape <- igraph.check.shapes(params("vertex", "shape"))
 
@@ -724,30 +726,39 @@ plot.igraph <- function(
   y <- layout[, 2] +
     label.dist * sin(-label.degree) * (vertex.size + 6 * 8 * log10(2)) / 200
   if (vc > 0) {
-    if (length(label.family) == 1) {
-      text(
-        x,
-        y,
-        labels = labels,
-        col = label.color,
-        family = label.family,
-        font = label.font,
-        cex = label.cex
-      )
-    } else {
-      if1 <- function(vect, idx) if (length(vect) == 1) vect else vect[idx]
-      sapply(seq_len(vcount(graph)), function(v) {
+    label.col <- rep(label.color, length.out = vc)
+    label.fam <- rep(label.family, length.out = vc)
+    label.fnt <- rep(label.font, length.out = vc)
+    label.cex <- rep(label.cex, length.out = vc)
+    label.ang <- rep(label.angle, length.out = vc)
+    label.adj <- rep(list(label.adj), length.out = vc)
+    label.text <- rep(labels, length.out = vc)
+
+    # Draw vertex labels
+    invisible(mapply(
+      function(x0, y0, lbl, col, fam, fnt, cex, srt, adj) {
         text(
-          x[v],
-          y[v],
-          labels = if1(labels, v),
-          col = if1(label.color, v),
-          family = if1(label.family, v),
-          font = if1(label.font, v),
-          cex = if1(label.cex, v)
+          x0,
+          y0,
+          labels = lbl,
+          col = col,
+          family = fam,
+          font = fnt,
+          cex = cex,
+          srt = srt,
+          adj = adj
         )
-      })
-    }
+      },
+      x,
+      y,
+      label.text,
+      label.col,
+      label.fam,
+      label.fnt,
+      label.cex,
+      label.ang,
+      label.adj
+    ))
   }
   rm(x, y)
   invisible(NULL)

R/plot.common.R

@@ -225,6 +225,13 @@
 #'
 #'   The default value is `black`.
 #' }
+#' \item{label.angle}{
+#'   The rotation of the vertex labels, in degrees. Corresponds to the `srt` parameter of [graphics::text()].
+#' }
+#' \item{label.adj}{
+#'   one or two numeric values, giving the horizontal and vertical adjustment of the vertex labels. See also `adj` in [graphics::text()].
+#' }
+
 #' \item{size.scaling}{
 #'   Switches between absolute vertex sizing (FALSE,default) and relative (TRUE).
 #'   If FALSE, `vertex.size` and `vertex.size2` are used as is.
@@ -4847,6 +4854,8 @@ i.vertex.default <- list(
   label.family = "serif",
   label.font = 1,
   label.cex = 1,
+  label.angle = 0,
+  label.adj = NULL,
   frame.color = "black",
   frame.width = 1,
   shape = "circle",

tests/testthat/test-plot.R

@@ -132,7 +132,26 @@ test_that("Edges stop at outside of rectangle node", {
   vdiffr::expect_doppelganger("rectangle-edges", rectangle_edges)
 })
 
+test_that("Vertex label rotation works", {
+  skip_if_not_installed("vdiffr")
+
+  label_rotate <- function() {
+    g <- make_ring(5, directed = FALSE, circular = FALSE)
+    V(g)$label <- c("AAAAA", "BBBBB", "CCCCC","DDDDD", "EEEEE")
+    g$layout <- cbind(1:5, rep(1, 5))
+    plot(
+      g,
+      vertex.label.angle = c(90, 90, 270, 270, 90),
+      vertex.label.adj = c(1.1,0.5)
+    )
+  }
+
+  vdiffr::expect_doppelganger("label-rotate", label_rotate)
+})
+
 test_that("Arrow drawing works correctly", {
+  skip_if_not_installed("vdiffr")
+
   standard_arrow <- function() {
     g <- make_graph(c(1, 2, 1, 3, 2, 4), directed = TRUE)
     g$layout <- cbind(1:4, rep(0, 4))