geophys (version 1.3-6)

vecproj: Vector Projection

Description

Vector Projection information, such as angle and distances between points

Usage

vecproj(P1, P2)

Arguments

P1

Point 1

P2

Point 2

Value

• cang=cang, angrad=angrad, angdeg=angdeg, dis1=d1, dis2=d2
• cang
  cosine of angle between points
• angrad
  angle, radians
• angdeg
  angle, degrees
• dis1
  distance
• dis2
  distance

Details

The distances returned are the legs of right right triangles where the cosine of the angle is used to get the projection distance of the opposite side on the specified direction. See the example for an illustration.

See Also

perpproj

Examples

P1 = c(2, 3)
P2 = c(5, 2)


I = vecproj(P1, P2)


plot(c(0, P1[1], P2[1]), c(0, P1[2], P2[2]), asp=1, ann=FALSE)

arrows(0, 0, P1[1],  P1[2], length=.1)
arrows(0, 0,  P2[1],  P2[2], length=.1)

text(P1[1],  P1[2], "Point 1", pos=3)
text(P2[1],  P2[2], "Point 2", pos=3)

j1 = atan2(P1[2], P1[1])*180/pi
j2 = atan2(P2[2], P2[1])*180/pi

L1 = vlength(P1)
L2 = vlength(P2)

A = GEOmap::darc(L1*.2, j1, j2, 0, 0, n=1)

lines(A)
an = length(A$x)
arrows(A$x[an-1] , A$y[an-1] ,A$x[an] , A$y[an] ,  length=.08 )

text(A$x[an/2] , A$y[an/2], labels=format(I$angdeg, digits=4)  , pos=4)


 V1 = c( 0,P1[1], 0,  P1[2])
   V2 = c( 0,P2[1], 0,  P2[2])
  

    PP = perpproj( V1, V2, add=FALSE  )

arrows(P1[1],P1[2],PP$P2[1], PP$P2[2],  length=.07, lty=2, col='red') 
arrows(P2[1],P2[2],PP$P1[1], PP$P1[2],  length=.07, lty=2, col='blue') 

 labelLine( c(0, 0) , PP$P2 , lab="dis1", dinch = .25, aty=1,
acol='blue', above=FALSE  )


 labelLine( c(0, 0) , PP$P1 , lab="dis2", dinch = .25, aty=1,
acol='blue'  )