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Recursive curve simplification.

Source: R/simplify.R
fm_simplify.Rd

[Experimental] Simplifies polygonal curve segments by joining nearly co-linear segments.

Uses a variation of the binary splitting Ramer-Douglas-Peucker algorithm, with an ellipse of half-width eps ellipse instead of a rectangle, motivated by prediction ellipse for Brownian bridge.

Usage

fm_simplify(x, eps = NULL, eps_rel = NULL, ...)

Arguments

x

An fm_segm() object.

eps

Absolute straightness tolerance. Default NULL, no constraint.

eps_rel

Relative straightness tolerance. Default NULL, no constraint.

...

Currently unused.

Value

The simplified fm_segm() object.

Details

Variation of Ramer-Douglas-Peucker. Uses width epsilon ellipse instead of rectangle, motivated by prediction ellipse for Brownian bridge.

References

Ramer, Urs (1972). "An iterative procedure for the polygonal approximation of plane curves". Computer Graphics and Image Processing. 1 (3): 244–256. doi:10.1016/S0146-664X(72)80017-0

Douglas, David; Peucker, Thomas (1973). "Algorithms for the reduction of the number of points required to represent a digitized line or its caricature". The Canadian Cartographer. 10 (2): 112–122. doi:10.3138/FM57-6770-U75U-7727

See also

Other object creation and conversion: fm_as_fm(), fm_as_lattice_2d(), fm_as_mesh_1d(), fm_as_mesh_2d(), fm_as_segm(), fm_as_sfc(), fm_as_tensor(), fm_lattice_2d(), fm_mesh_1d(), fm_mesh_2d(), fm_segm(), fm_tensor()

Author

Finn Lindgren finn.lindgren@gmail.com

Examples

theta <- seq(0, 2 * pi, length.out = 1000)
(segm <- fm_segm(cbind(cos(theta), sin(theta)),
  idx = seq_along(theta)
))
#> fm_segm object:
#>   999 boundary edges
#>   Bounding box = (-0.9999951, 1.0000000) x (-0.9999988, 0.9999988) x (0,0)
(segm1 <- fm_simplify(segm, eps_rel = 0.1))
#> fm_segm object:
#>   16 boundary edges (1 group: 0)
#>   Bounding box = (-0.9999951, 1.0000000) x (-0.9999988, 0.9999889) x (0,0)
(segm2 <- fm_simplify(segm, eps_rel = 0.2))
#> fm_segm object:
#>   8 boundary edges (1 group: 0)
#>   Bounding box = (-0.9999951, 1.0000000) x (-0.9999988, 0.9999889) x (0,0)
plot(segm)
lines(segm1, col = 2)
lines(segm2, col = 3)


(segm <- fm_segm(cbind(theta, sin(theta * 4)),
  idx = seq_along(theta)
))
#> fm_segm object:
#>   999 boundary edges
#>   Bounding box = (0.000000,6.283185) x (-0.9999988, 0.9999988) x (0,0)
(segm1 <- fm_simplify(segm, eps_rel = 0.1))
#> fm_segm object:
#>   73 boundary edges (1 group: 0)
#>   Bounding box = (0.000000,6.283185) x (-0.9999988, 0.9999988) x (0,0)
(segm2 <- fm_simplify(segm, eps_rel = 0.2))
#> fm_segm object:
#>   17 boundary edges (1 group: 0)
#>   Bounding box = (0.000000,6.283185) x (-0.9995538, 0.9994549) x (0,0)
plot(segm)
lines(segm1, col = 2)
lines(segm2, col = 3)