R 将线旋转到正北或垂直方向
我有一个数据集,其中包含对角运行的多段线,我想将这些线旋转到垂直或正北,以便正确显示x轴数据。我已经看过罗德里格斯公式,但它的方式超过我的头,想知道他们是否是一个包在R,我可以使用。请参见下面的示例,我需要对其进行旋转R 将线旋转到正北或垂直方向,r,ggplot2,sf,R,Ggplot2,Sf,我有一个数据集,其中包含对角运行的多段线,我想将这些线旋转到垂直或正北,以便正确显示x轴数据。我已经看过罗德里格斯公式,但它的方式超过我的头,想知道他们是否是一个包在R,我可以使用。请参见下面的示例,我需要对其进行旋转 library(sf) library(ggplot2) ex<-structure(list(OBJECTID = c(10526, 10913), geometry = structure(list( structure(c(-103.47406, -103.
library(sf)
library(ggplot2)
ex<-structure(list(OBJECTID = c(10526, 10913), geometry = structure(list(
structure(c(-103.47406, -103.46268, 31.47367, 31.48499), .Dim = c(2L,
2L), class = c("XY", "LINESTRING", "sfg")), structure(c(-103.46525,
-103.4788333, 31.4879722000001, 31.4748056), .Dim = c(2L,
2L), class = c("XY", "LINESTRING", "sfg"))), n_empty = 0L, crs = structure(list(
epsg = 4267L, proj4string = "+proj=longlat +datum=NAD27 +no_defs"), class = "crs"), class = c("sfc_LINESTRING",
"sfc"), precision = 0, bbox = structure(c(xmin = -103.4788333,
ymin = 31.47367, xmax = -103.46268, ymax = 31.4879722000001), class = "bbox"))), row.names = c(NA,
-2L), sf_column = "geometry", agr = structure(c(OBJECTID = NA_integer_), .Label = c("constant",
"aggregate", "identity"), class = "factor"), class = c("sf",
"tbl_df", "tbl", "data.frame"))
ggplot(ex)+geom_sf()
库(sf)
图书馆(GG2)
ex假设所有直线平行,旋转点是所有直线的质心,一种方法是
找到直线的质心
找到直线和正北方向之间的方位
围绕质心旋转每个坐标
完成了
库(sf)
图书馆(sfheaders)
图书馆(GG2)
图书馆(地球圈)
##找到线的中心
我相信它需要在离原点最近的点附近。如果多段线的长度明显不同,围绕中点或任何其他点旋转都会有问题。就我而言,这不是一个很好的原点定义。我只想把线旋转到垂直方向,但保持两条线之间的距离不变。我已经更新了,加入了我所追求的东西的图表。左图为原始方位/方向。正确的两个情节中的任何一个都是我想要做的。可能在直线组的中点旋转?是的,它们将始终平行或接近平行。
library(sf)
library(sfheaders)
library(ggplot2)
library(geosphere)
## get the centre of the lines
centre <- sf::st_centroid( sf::st_union( ex ) )
## remove class so we just have coordinates as a vector
centre <- unclass( centre[[1]] )
## get each coordinate of the lines. These will each be rotated
coords <- sf::st_coordinates( ex )
## to know the angle of rotation, we need to know due-north from a given point
## under the assumption all lines are parallel, we just need the bearing between the
## start of a line and the end
##
## you're using lon / lat values, so we can use geosphere package to get the bearing
bearing <- geosphere::bearing(
p1 = coords[1, c("X","Y")]
, p2 = coords[2, c("X","Y")]
)
theta <- bearing * pi / 180 ## in radians
#' rotate
#' function to rotate x and y coordinates around a point
#' theta - angle of rotation
#' p - point(s) to rotate
#' centre - centre point
rotate <- function( theta, p, centre ) {
new_x <- cos( theta ) * ( p[, 1] - centre[1] ) - sin( theta ) * ( p[, 2] - centre[2] ) + centre[1]
new_y <- sin( theta ) * ( p[, 1] - centre[1] ) + cos( theta ) * ( p[, 2] - centre[2] ) + centre[2]
return( matrix( c( new_x, new_y ), ncol = 2 ) )
}
## calculate the rotated points
coords_new <- rotate( theta, coords, centre )
## we've kept order in tact, so we can cbind the L1 id back on
coords_new <- cbind( coords_new, coords[, "L1"])
## new sf object (using library(sfheaders) )
sf_new <- sfheaders::sf_linestring( obj = coords_new, linestring_id = 3)
sf::st_crs( sf_new ) <- sf::st_crs( ex )
## plot to verify
ggplot() + geom_sf( data = sf_new ) +
geom_sf( data = ex ) +
geom_sf( data = sf::st_centroid( sf::st_union( ex ) ) )