diag2edge {pgirmess}

Computes the edge of a square from its diagonal

Description

Computes the edge of a square from its diagonal.

Usage

diag2edge(cordseg)

Arguments

cordseg

The diagonal coordinates. This can be a vector c(x1,y1,x2,y2), a 2 x 2 matrix or a data.frame (each line a coordinate)

Details

The first point coordinates are the left top of the diagonal. The other coordinates computed are the other top of the square edge. Can be used e.g. to pass a square edge to pave in order to compute a sampling grid.

Value

A 2x2 matrix of points coordinates

See Also

pave

Examples

# diagonal sloping up
coord<-matrix(c(20,20,90,90),nr=2,byrow=TRUE)
plot(coord,type="n",xlim=c(0,100),ylim=c(0,110),asp=1)
lines(coord,lty=2)
# square edge
lines(diag2edge(coord),col="red")

# diagonal sloping down
coord<-matrix(c(20,90,90,20),nr=2,byrow=TRUE)
plot(coord,type="n",xlim=c(0,100),ylim=c(0,110),asp=1)
lines(coord,lty=2)
# square edge
lines(diag2edge(coord),col="red")

# diagonal vertical
coord<-matrix(c(20,90,20,20),nr=2,byrow=TRUE)
plot(coord,type="n",xlim=c(0,100),ylim=c(0,110),asp=1)
lines(coord,lty=2)
# square edge
lines(diag2edge(coord),col="red")