IdentifyA: Identify Points in Plot Lying Within a Rectangle or Polygon

Description

Find all the points lying either in a rectangle area spanned by an upper left and a bottom-right point or by a polygon area consisting of any number of points defined by point and click.

Usage

IdentifyA(x, ...)
# S3 method for formula
IdentifyA (formula, data, subset, poly = FALSE, ...)
# S3 method for default
IdentifyA (x, y = NULL, poly = FALSE, ...)

Value

Index vector with the points lying within the selected area. The coordinates are returned as text in the attribute "cond".

Arguments

x, y: x and y values of the points used to create the plot.
formula: a formula, such as y ~ x specifying x and y values.
Here the formula must be entered that was used to create the scatterplot.
data: a data frame (or list) from which the variables in formula should be taken.
subset: an optional vector specifying a subset of observations to be used.
poly: logical. Defines if a polygon or a rectangle should be used to select the points. Default is rectangle. If a polygon should be used, set this argument to TRUE and select all desired points. The polygon will be closed automatically when finished.
...: Other arguments to be passed to IdentifyA.

Author

Andri Signorell <andri@signorell.net>

Examples

Run this code

if (FALSE) {
# run the example via copy and paste

plot(temperature ~ delivery_min, data=d.pizza)
idx <- IdentifyA(temperature ~ delivery_min, data=d.pizza)

# you selected the following points
d.pizza[idx,]
points(temperature ~ delivery_min, data = d.pizza[idx,], col="green")

# use the attr("cond") for subsets in code
attr(idx, "cond")

# create a group variable for the found points
d.pizza$grp <- seq(nrow(d.pizza)) %in% idx

# try the polygon option
idx <- IdentifyA(temperature ~ delivery_min, data=d.pizza, poly=TRUE)
points(temperature ~ delivery_min, data = d.pizza[idx,], col="red")
}