matlib (version 0.9.8)

vectors: Draw geometric vectors in 2D

Description

This function draws vectors in a 2D plot, in a way that facilitates constructing vector diagrams. It allows vectors to be specified as rows of a matrix, and can draw labels on the vectors.

Usage

vectors(
  X,
  origin = c(0, 0),
  lwd = 2,
  angle = 13,
  length = 0.15,
  labels = TRUE,
  cex.lab = 1.5,
  pos.lab = 4,
  frac.lab = 1,
  ...
)

Value

none

Arguments

X

a vector or two-column matrix representing a set of geometric vectors; if a matrix, one vector is drawn for each row

origin

the origin from which they are drawn, a vector of length 2.

lwd

line width(s) for the vectors, a constant or vector of length equal to the number of rows of X.

angle

the angle argument passed to arrows determining the angle of arrow heads.

length

the length argument passed to arrows determining the length of arrow heads.

labels

a logical or a character vector of labels for the vectors. If TRUE and X is a matrix, labels are taken from rownames(X). If NULL, no labels are drawn.

cex.lab

character expansion applied to vector labels. May be a number or numeric vector corresponding to the the rows of X, recycled as necessary.

pos.lab

label position relative to the label point as in text, recycled as necessary.

frac.lab

location of label point, as a fraction of the distance between origin and X, recycled as necessary. Values frac.lab > 1 locate the label beyond the end of the vector.

...

other arguments passed on to graphics functions.

See Also

arrows, text

Other vector diagrams: Proj(), arc(), arrows3d(), circle3d(), corner(), plot.regvec3d(), pointOnLine(), regvec3d(), vectors3d()

Examples

# shows addition of vectors
u <- c(3,1)
v <- c(1,3)
sum <- u+v

xlim <- c(0,5)
ylim <- c(0,5)
# proper geometry requires asp=1
plot( xlim, ylim, type="n", xlab="X", ylab="Y", asp=1)
abline(v=0, h=0, col="gray")

vectors(rbind(u,v,`u+v`=sum), col=c("red", "blue", "purple"), cex.lab=c(2, 2, 2.2))
# show the opposing sides of the parallelogram
vectors(sum, origin=u, col="red", lty=2)
vectors(sum, origin=v, col="blue", lty=2)

# projection of vectors
vectors(Proj(v,u), labels="P(v,u)", lwd=3)
vectors(v, origin=Proj(v,u))
corner(c(0,0), Proj(v,u), v, col="grey")