Description Details See Also Examples

Create contour lines for a non regular series of points, potentially from a non-regular canvas.

The `contoureR`

package executes linear interpolation on a delaunay triangulated
mesh strung between three-dimensional (3D) points supplied by the user. Contours are calculated
across the surface constrained by the convex hull of the supplied data.

Usually, the well known functions such as `contourLines`

from the `grDevices`

package, expect (or rather, require) data to be regular, this means that a rectangular array or matrix of
`x`

and `y`

coordinate pairs, each with a corresponding `z`

value is to be modelled – that
is to say the cartesian product of a numeric vector of `x`

values of length `n`

,
with a numeric vector of `y`

values having length `m`

, used to produce a set of
`(m x n)`

unique points that have been concurrently provided with `exactly (m x n) z values`

.

By restricting values to the above format, this in turn limits the region of analysis to square/rectangular
canvasses (ie plane defined by geometric and orthogonal vectors parallel to the `x`

and `y`

axes and range bound by the `[xmin,xmax]`

and `[ymin,ymax]`

in the above `x`

and `y`

input numeric vectors, respectively).
This restriction, from time-to-time, can be very inconvenient, and is a primary objective and purpose for
the creation of this package.

As suggested in the previous paragraph, the `contoureR`

package, on the other hand, has no such
orthogonality / regularity requirement and can therefore be applied over obscurely shaped regions such as
triangles, circles, polygons and the like. To demonstrate this, in the example
provided on the current page, an equation is contoured, where firstly the `x`

and `y`

data is
randomly selected (non regular), and then the set of values is subsequently constrained by a
bounding (limiting) circle.

Note, for the moment, the only restriction is that for polygon-type regions to be
modelled, then these regions must **not** have holes, since these will be filled coarsely when the
Deleaunaymesh gets generated, however, in future revisions, this obstacle should be easily addressed via
parameter defining a manual exclusion list of points.

`getContourLines`

, `contourLinesR`

and `contourWalker`

1 2 3 4 5 6 7 8 9 10 11 12 | ```
# Contour Lines for a Function, Constrained to a limited domain
# Example of the provision of non-regular data
library(contoureR)
library(ggplot2)
a = -2; b = +2; n = 150
x = runif(n*n,a,b)
y = runif(n*n,a,b)
df = data.frame(x,y)
df$z = with(df,-x*y*exp(-x^2-y^2))
df.sub = subset(df,x^2 + y^2 < 2)
df.cnt = getContourLines(df.sub,nlevels=20)
ggplot(data=df.cnt,aes(x,y,group=Group,colour=z)) + geom_path() + theme_bw()
``` |

```
Loading required package: geometry
Loading required package: magic
Loading required package: abind
```

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