# boundary_Grid: Find boundary points in a 'Grid' object In smint: Smooth Multivariate Interpolation for Gridded and Scattered Data

## Description

Find boundary points in a `Grid` object.

## Usage

 `1` ```boundary_Grid(x, type = c("data.frame", "array", "index")) ```

## Arguments

 `x` An object with class `"Grid"`. `type` The wanted type of result.

## Details

When `type` is `"data.frame"`, the returned object is a data frame containing only the boundary points. When `type` is `"array"` the result is a logical array with its elements in correspondence with the `index` slot of the object. Finally, when `type` is `"index"`, the result is an integer vector giving the indices of the boundary points in the order of the nodes defined by the object. This order is the one used by the `as.data.frame` coercion.

## Value

An object describing the boundary points. See Details.

## Note

Remind that when using the `plot` method for a `Grid` object, some nodes are generally hidden because several points have the same projection when they are shown in a two-dimensional scatterplot.

When one or more of the levels has length <= 2, all points of the grid are boundary points!

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22``` ```## define a Grid object myGD <- Grid(nlevels = c(3, 4)) bd <- boundary_Grid(myGD, type = "index") ## use a different color for boundary points cols <- rep("black", length(myGD)) cols[bd] <- "red" plot(myGD, col = cols, pch = 16, cex = 2, main = "Boundary points") ## repeat this after a generalised transposition myGD2 <- aperm(myGD, perm = c(2, 1)) bd2 <- boundary_Grid(myGD2, type = "index") cols2 <- rep("black", length(myGD2)) cols2[bd2] <- "red" plot(myGD2, col = cols2, pch = 16, cex = 2, main = "Boundary points") ## 3-dimensional myGD3 <- Grid(nlevels = c("x" = 3, "y"= 4, "z" = 6)) bd3 <- boundary_Grid(myGD3, type = "index") cols3 <- rep("black", length(myGD3)) cols3[bd3] <- "red" plot(myGD3, jitter = TRUE, col = cols3, pch = 16, cex = 2, main = "Boundary points") ```

smint documentation built on April 14, 2017, 1:49 p.m.