subset.ppp

0th

Percentile

Subset of Point Pattern Satisfying A Condition

Given a point pattern, return the subset of points which satisfy a specified condition.

Keywords
manip, spatial
Usage
## S3 method for class 'ppp':
subset(x, subset, select, \dots)

## S3 method for class 'pp3': subset(x, subset, select, \dots)

## S3 method for class 'lpp': subset(x, subset, select, \dots)

## S3 method for class 'ppx': subset(x, subset, select, \dots)

Arguments
x
A point pattern (object of class "ppp", "lpp", "pp3" or "ppx").
subset
Logical expression indicating which points are to be kept. The expression may involve the names of spatial coordinates (x, y, etc), the marks, and (if there is more than one column of marks) the names
select
Expression indicating which columns of marks should be kept.
...
Ignored.
Details

This is a method for the generic function subset. It extracts the subset of points of x that satisfy the logical expression subset, and retains only the columns of marks that are specified by the expression select. The result is always a point pattern.

The argument subset determines the subset of points that will be extracted. It should be a logical expression. It may involve the variable names x and y representing the Cartesian coordinates; the names of other spatial coordinates or local coordinates; the name marks representing the marks; and (if there is more than one column of marks) the names of individual columns of marks. The default is to keep all points.

The argument select determines which columns of marks will be retained (if there are several columns of marks). It should be an expression involving the names of columns of marks (which will be interpreted as integers representing the positions of these columns). For example if there are columns of marks named A to Z, then select=D:F is a valid expression and means that columns D, E and F will be retained. Similarly select=-(A:C) is valid and means that columns A to C will be deleted. The default is to retain all columns.

Setting subset=FALSE will produce an empty point pattern (i.e. containing zero points) in the same window as x. Setting select=FALSE or select= -marks will remove all the marks from x. The result is always a point pattern, of the same class as x. Spatial coordinates (and local coordinates) are always retained. To extract only some columns of marks or coordinates as a data frame, use subset(as.data.frame(x), ...)

Value

  • A point pattern of the same class as x, in the same spatial window as x. The result is a subset of x, possibly with some columns of marks removed.

See Also

subset, [.ppp

Aliases
  • subset.ppp
  • subset.pp3
  • subset.lpp
  • subset.ppx
Examples
plot(subset(cells, x > 0.5))

 subset(amacrine, marks == "on")

 subset(redwood, nndist(redwood) > 0.04)

 subset(finpines, select=height)

 subset(finpines, diameter > 2, height)

 subset(nbfires, year==1999 & ign.src == "campfire",
                 select=cause:fnl.size)

 v <- subset(chicago, x + y > 1100 & marks == "assault")

 a <- subset(rpoispp3(40), z > 0.5)
Documentation reproduced from package spatstat, version 1.42-2, License: GPL (>= 2)

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