Have you every wanted to generate geometric structures from data.frames, but independent of any R classes, attributes or libraries?
No? Ok, this library isn’t for you.
But if you answered ‘yes’, this might be of interest.
When one thinks of ‘shape’ objects in R, the current standard / typical structures are
(in reality you can have more than just x & y columns)
But constructing these can sometimes be a bit fiddly.
So my goal of this package is to take away the pain of building shapes. I want to accept any base R data object and convert it into the required shape
Take a data.frame
df <- data.frame(
id = c(1,1,1,1,1,2,2,2,2,2)
, x = 1:10
, y = 10:1
)
df
# id x y
# 1 1 1 10
# 2 1 2 9
# 3 1 3 8
# 4 1 4 7
# 5 1 5 6
# 6 2 6 5
# 7 2 7 4
# 8 2 8 3
# 9 2 9 2
# 10 2 10 1
You can make two “LINE”* objects by splitting this into a list of matrices
gm_geometries(
obj = df
, geometry_cols = c("x","y")
, id_cols = c("id")
)
# [[1]]
# [,1] [,2]
# [1,] 1 10
# [2,] 2 9
# [3,] 3 8
# [4,] 4 7
# [5,] 5 6
#
# [[2]]
# [,1] [,2]
# [1,] 6 5
# [2,] 7 4
# [3,] 8 3
# [4,] 9 2
# [5,] 10 1
*I’ve put “LINE” in quotes because this doesn’t have to be called a LINE, it’s just that a LINE is typically represented by a matrix in R.
And if you send it a class_attribute
, you can make it into whatever
type of object you want
gm_geometries(
obj = df
, geometry_cols = c("x","y")
, id_cols = c("id")
, class_attributes = list(class = "my_new_shape", other = "really_awesome_shape")
)
# [[1]]
# [,1] [,2]
# [1,] 1 10
# [2,] 2 9
# [3,] 3 8
# [4,] 4 7
# [5,] 5 6
# attr(,"class")
# [1] "my_new_shape"
# attr(,"other")
# [1] "really_awesome_shape"
#
# [[2]]
# [,1] [,2]
# [1,] 6 5
# [2,] 7 4
# [3,] 8 3
# [4,] 9 2
# [5,] 10 1
# attr(,"class")
# [1] "my_new_shape"
# attr(,"other")
# [1] "really_awesome_shape"
And I’m building it as an interface package. That is, it’s all being written in C++ header files, so you can link to these header files from your own package.
When you build a package, if you want to use C++ code from another
package, you have to let the compiler know. In an R package, you do
this by specifying a LinkingTo
value in the DESCRIPTION.
Take for example, the LinkingTo section in the DESCRIPTION field of this package
SystemRequirements: C++11
LinkingTo:
Rcpp
Imports:
Rcpp
This tells the compiler I want to link to Rcpp’s. Which means I can use all the Rcpp code by including whichever header file I want.
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