# vecproj: Vector Projection In geophys: Geophysics, Continuum Mechanics, Mogi Models, Gravity

## Description

Vector Projection information, such as angle and distances between points

## Usage

 `1` ```vecproj(P1, P2) ```

## Arguments

 `P1` Point 1 `P2` Point 2

## 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.

## Value

 `cang` cosine of angle between points `angrad` angle, radians `angdeg` angle, degrees `dis1` distance `dis2` distance

## Author(s)

Jonathan M. Lees<[email protected]>

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45``` ```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' ) ```