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This function generates points in one or two dimensions with a weight attached to each point. The weighted sum of a function evaluated at these points is the integral of that function approximated by linear basis functions. The parameter samplers describes the area(s) integrated over.

In case of a single dimension samplers is supposed to be a two-column matrix where each row describes the start and end points of the interval to integrate over. In the two-dimensional case samplers can be either a SpatialPolygon, an inla.mesh or a SpatialLinesDataFrame describing the area to integrate over. If a SpatialLineDataFrame is provided, it has to have a column called 'weight' in order to indicate the width of the line.

## Value

A data.frame or SpatialPointsDataFrame of 1D and 2D integration points, respectively.

## Author

Fabian E. Bachl bachlfab@gmail.com and finn.lindgren@gmail.com

## Examples

# \donttest{
if (require("INLA", quietly = TRUE) &&
require("ggplot2", quietly = TRUE)) {
# Create 50 integration points covering the dimension 'myDim' between 0 and 10.

ips <- ipoints(c(0, 10), 50, name = "myDim")
plot(ips)

# Create integration points for the two intervals [0,3] and [5,10]

ips <- ipoints(matrix(c(0, 3, 5, 10), nrow = 2, byrow = TRUE), 50)
plot(ips)

# Convert a 1D mesh into integration points
mesh <- inla.mesh.1d(seq(0, 10, by = 1))
ips <- ipoints(mesh, name = "time")
plot(ips)

# Obtain 2D integration points from a SpatialPolygon

data(gorillas, package = "inlabru")
ips <- ipoints(gorillas$boundary) ggplot() + gg(gorillas$boundary) +
gg(ips, aes(size = weight))

#' Project integration points to mesh vertices

ips <- ipoints(gorillas$boundary, domain = gorillas$mesh)
ggplot() +
gg(gorillas$mesh) + gg(gorillas$boundary) +
gg(ips, aes(size = weight))

# Turn a 2D mesh into integration points

ips <- ipoints(gorillas$mesh) ggplot() + gg(gorillas$boundary) +
gg(ips, aes(size = weight))
}

#> Warning: Computing integration points from polygon; specify a mesh for better numerical control.
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#> Regions defined for each Polygons

# }