Crop, rotate, flip, and transpose a GraphSpace

Accessory functions to spatially transform a normalized GraphSpace object. cropGraphSpace() subsets the plotting area to a rectangular region; rotateGraphSpace() rotates by a quarter turn; flipGraphSpace() mirrors horizontally or vertically; transposeGraphSpace() swaps the x and y axes.

Usage

# S4 method for class 'GraphSpace'
cropGraphSpace(gs, xmin = 0, xmax = 1, ymin = 0, ymax = 1, verbose = TRUE)

# S4 method for class 'GraphSpace'
flipGraphSpace(gs, vertical = FALSE, persist = .is_raw(gs), verbose = TRUE)

# S4 method for class 'GraphSpace'
rotateGraphSpace(gs, clockwise = FALSE, persist = .is_raw(gs), verbose = TRUE)

# S4 method for class 'GraphSpace'
transposeGraphSpace(gs, persist = .is_raw(gs), verbose = TRUE)

Arguments

gs: A normalized GraphSpace object.
xmin: A single number in [0,1] specifying the lower x-boundary of the plotting area.
xmax: A single number in [0,1] specifying the upper x-boundary of the plotting area.
ymin: A single number in [0,1] specifying the lower y-boundary of the plotting area.
ymax: A single number in [0,1] specifying the upper y-boundary of the plotting area.
verbose: A single logical value specifying to display detailed messages (when verbose=TRUE) or not (when verbose=FALSE).
vertical: Logical; if FALSE (default), the flip is horizontal (mirror left-right); if TRUE, vertical (mirror top-bottom). (flipGraphSpace only).
persist: Logical; whether the transformation persists through re-normalization. Defaults to TRUE before normalization, FALSE after.
clockwise: Logical; if FALSE (default), the 90-degree turn is counter-clockwise; if TRUE, clockwise (rotateGraphSpace only).

Value

A GraphSpace object with updated nodes and canvas slots.

Details

cropGraphSpace() subsets a normalized graph space to a specific region defined by the cropping boundaries. It recalculates node positions and background image boundaries to maintain spatial consistency after cropping, and drops nodes (and edges) that fall outside the window.

rotateGraphSpace(), flipGraphSpace(), and transposeGraphSpace() are all exact, a coordinate/pixel permutation, with no resampling, no interpolation, and no risk of misaligning nodes against the background image. rotateGraphSpace() is restricted to a single 90-degree turn: apply it again to its own output for 180 or 270 degrees, e.g. rotateGraphSpace(rotateGraphSpace(gs)) for 180 degrees. Combine all three with each other to reach any of the 8 symmetries of a square.

Note

This is an accessory function typically called during the preprocessing of GraphSpace objects before rendering.

Examples

library(RGraphSpace)
library(igraph)

# Create a star graph
gtoy1 <- make_full_graph(30)

# Create a GraphSpace
gs <- GraphSpace(gtoy1)
#> Validating the 'igraph' object...
#> Vertex attributes 'x' and 'y' missing; computing layout...
#> Vertex attribute 'name' missing; assigning names... 
#> Ignoring graph-level attributes: 'name', 'loops'
#> Creating a 'GraphSpace' object...

gs <- normalizeGraphSpace(gs)
#> Normalizing node coordinates to graph space...

gs_crop <- cropGraphSpace(gs, ymax = 0.5)
#> Cropping graph space to x in [0, 1], y in [0, 0.5]...
gs_rot90 <- rotateGraphSpace(gs)
#> Rotating normalized coordinates 90 degrees counter-clockwise...
gs_flip <- flipGraphSpace(gs)
#> Flipping normalized coordinates horizontally...
gs_t <- transposeGraphSpace(gs)
#> Transposing normalized coordinates...

plotGraphSpace(gs, add.labels = TRUE)


plotGraphSpace(gs_crop, add.labels = TRUE)