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20 hours ago •
r-spatial
r-spatial
st_graticule() produces hundreds of tiny line segments when break falls onto bbox boundary
Originally reported for ggplot2 here: https://github.com/tidyverse/ggplot2/issues/3938
When an axis break falls exactly onto a bounding box boundary, st_graticule() produces hundreds of tiny line segments. While ggplot2 should probably be tolerant to this, the result is strange nonetheless, and it would be good if it could be fixed.
# works fine
bbox <- c(-18.4, -12.4, -9.6, -3.6)
sf::st_graticule(
bbox,
crs = NULL,
lat = NULL,
lon = NULL,
datum = sf::st_crs(4326),
ndiscr = 100
)
#> Simple feature collection with 10 features and 10 fields
#> geometry type: LINESTRING
#> dimension: XY
#> bbox: xmin: -18.4 ymin: -12.4 xmax: -9.6 ymax: -3.6
#> CRS: NA
#> degree type degree_label geometry x_start y_start
#> 2 -18 E -18 LINESTRING (-18 -12.4, -18 ... -18.0 -12.4
#> 3 -16 E -16 LINESTRING (-16 -12.4, -16 ... -16.0 -12.4
#> 4 -14 E -14 LINESTRING (-14 -12.4, -14 ... -14.0 -12.4
#> 5 -12 E -12 LINESTRING (-12 -12.4, -12 ... -12.0 -12.4
#> 6 -10 E -10 LINESTRING (-10 -12.4, -10 ... -10.0 -12.4
#> 9 -12 N -12 LINESTRING (-18.4 -12, -18.... -18.4 -12.0
#> 10 -10 N -10 LINESTRING (-18.4 -10, -18.... -18.4 -10.0
#> 11 -8 N -8 LINESTRING (-18.4 -8, -18.3... -18.4 -8.0
#> 12 -6 N -6 LINESTRING (-18.4 -6, -18.3... -18.4 -6.0
#> 13 -4 N -4 LINESTRING (-18.4 -4, -18.3... -18.4 -4.0
#> x_end y_end angle_start angle_end plot12
#> 2 -18.0 -3.6 90 90 TRUE
#> 3 -16.0 -3.6 90 90 TRUE
#> 4 -14.0 -3.6 90 90 TRUE
#> 5 -12.0 -3.6 90 90 TRUE
#> 6 -10.0 -3.6 90 90 TRUE
#> 9 -9.6 -12.0 0 0 TRUE
#> 10 -9.6 -10.0 0 0 TRUE
#> 11 -9.6 -8.0 0 0 TRUE
#> 12 -9.6 -6.0 0 0 TRUE
#> 13 -9.6 -4.0 0 0 TRUE
# creates hundreds of graticule lines
bbox <- c(-18, -12, -10, -4)
sf::st_graticule(
bbox,
crs = NULL,
lat = NULL,
lon = NULL,
datum = sf::st_crs(4326),
ndiscr = 100
)
#> Simple feature collection with 506 features and 10 fields
#> geometry type: LINESTRING
#> dimension: XY
#> bbox: xmin: -18 ymin: -12 xmax: -10 ymax: -4
#> CRS: NA
#> First 10 features:
#> degree type degree_label geometry x_start y_start
#> 1 -18 E -18 LINESTRING (-18 -12, -18 -1... -18 -12.00000
#> 1.1 -18 E -18 LINESTRING (-18 -11.91919, ... -18 -11.91919
#> 1.2 -18 E -18 LINESTRING (-18 -11.83838, ... -18 -11.83838
#> 1.3 -18 E -18 LINESTRING (-18 -11.75758, ... -18 -11.75758
#> 1.4 -18 E -18 LINESTRING (-18 -11.68, -18... -18 -11.68000
#> 1.5 -18 E -18 LINESTRING (-18 -11.67677, ... -18 -11.67677
#> 1.6 -18 E -18 LINESTRING (-18 -11.59596, ... -18 -11.59596
#> 1.7 -18 E -18 LINESTRING (-18 -11.51515, ... -18 -11.51515
#> 1.8 -18 E -18 LINESTRING (-18 -11.43434, ... -18 -11.43434
#> 1.9 -18 E -18 LINESTRING (-18 -11.36, -18... -18 -11.36000
#> x_end y_end angle_start angle_end plot12
#> 1 -18 -11.91919 90 90 TRUE
#> 1.1 -18 -11.83838 90 90 FALSE
#> 1.2 -18 -11.75758 90 90 FALSE
#> 1.3 -18 -11.68000 90 90 FALSE
#> 1.4 -18 -11.67677 90 90 FALSE
#> 1.5 -18 -11.59596 90 90 FALSE
#> 1.6 -18 -11.51515 90 90 FALSE
#> 1.7 -18 -11.43434 90 90 FALSE
#> 1.8 -18 -11.36000 90 90 FALSE
#> 1.9 -18 -11.35354 90 90 FALSE
# works fine, breaks are internal only
sf::st_graticule(
bbox,
crs = NULL,
lat = c(-10, -8, -6),
lon = c(-16, -14, -12),
datum = sf::st_crs(4326),
ndiscr = 100
)
#> Simple feature collection with 6 features and 10 fields
#> geometry type: LINESTRING
#> dimension: XY
#> bbox: xmin: -18 ymin: -12 xmax: -10 ymax: -4
#> CRS: NA
#> degree type degree_label geometry x_start y_start x_end
#> 1 -16 E -16 LINESTRING (-16 -12, -16 -1... -16 -12 -16
#> 2 -14 E -14 LINESTRING (-14 -12, -14 -1... -14 -12 -14
#> 3 -12 E -12 LINESTRING (-12 -12, -12 -1... -12 -12 -12
#> 4 -10 N -10 LINESTRING (-18 -10, -17.91... -18 -10 -10
#> 5 -8 N -8 LINESTRING (-18 -8, -17.919... -18 -8 -10
#> 6 -6 N -6 LINESTRING (-18 -6, -17.919... -18 -6 -10
#> y_end angle_start angle_end plot12
#> 1 -4 90 90 TRUE
#> 2 -4 90 90 TRUE
#> 3 -4 90 90 TRUE
#> 4 -10 0 0 TRUE
#> 5 -8 0 0 TRUE
#> 6 -6 0 0 TRUE
# problematic again, the breaks are right on the bounding box boundary
sf::st_graticule(
bbox,
crs = NULL,
lat = c(-12, -4),
lon = c(-18, -10),
datum = sf::st_crs(4326),
ndiscr = 100
)
#> Simple feature collection with 492 features and 10 fields
#> geometry type: LINESTRING
#> dimension: XY
#> bbox: xmin: -18 ymin: -12 xmax: -10 ymax: -4
#> CRS: NA
#> First 10 features:
#> degree type degree_label geometry x_start y_start
#> 1 -18 E -18 LINESTRING (-18 -12, -18 -1... -18 -12.00000
#> 1.1 -18 E -18 LINESTRING (-18 -11.91919, ... -18 -11.91919
#> 1.2 -18 E -18 LINESTRING (-18 -11.83838, ... -18 -11.83838
#> 1.3 -18 E -18 LINESTRING (-18 -11.75758, ... -18 -11.75758
#> 1.4 -18 E -18 LINESTRING (-18 -11.68, -18... -18 -11.68000
#> 1.5 -18 E -18 LINESTRING (-18 -11.67677, ... -18 -11.67677
#> 1.6 -18 E -18 LINESTRING (-18 -11.59596, ... -18 -11.59596
#> 1.7 -18 E -18 LINESTRING (-18 -11.51515, ... -18 -11.51515
#> 1.8 -18 E -18 LINESTRING (-18 -11.43434, ... -18 -11.43434
#> 1.9 -18 E -18 LINESTRING (-18 -11.36, -18... -18 -11.36000
#> x_end y_end angle_start angle_end plot12
#> 1 -18 -11.91919 90 90 TRUE
#> 1.1 -18 -11.83838 90 90 FALSE
#> 1.2 -18 -11.75758 90 90 FALSE
#> 1.3 -18 -11.68000 90 90 FALSE
#> 1.4 -18 -11.67677 90 90 FALSE
#> 1.5 -18 -11.59596 90 90 FALSE
#> 1.6 -18 -11.51515 90 90 FALSE
#> 1.7 -18 -11.43434 90 90 FALSE
#> 1.8 -18 -11.36000 90 90 FALSE
#> 1.9 -18 -11.35354 90 90 FALSE
Created on 2020-04-11 by the reprex package (v0.3.0)
Upon further reflection, ggplot2 is actually fully tolerant to these graticules (https://github.com/tidyverse/ggplot2/issues/3938#issuecomment-612563396), so fixing this issue is maybe not as urgent as it initially seemed to be. Nevertheless, if it can be fixed that'd be nice.