R: set a rotation matrix

rotmat2D {GEOmap} | R Documentation

## set a rotation matrix

### Description

set a rotation matrix

### Usage

    rotmat2D(alph)

### Arguments

`alph` | angle in radians

### Value

matrix for rotation in 2 dimensions

### Author(s)

Jonathan M. Lees<jonathan.lees@unc.edu>

### Examples

    ########  make an ellipse
     theta=seq(0,360,by=5)*pi/180

    r1 = 0.4
    r2 = 0.2

       m=matrix(rep(0,2*length(theta)),ncol=2)

     m[,1]=r1*cos(theta)
        m[,2]=r2*sin(theta)

    ##  make a dummy plot and draw ellipse

     plot(c(0, 1), c(0, 1), main = "this is a test", sub = "sutitle",
            xlab = "this is x", ylab = "this is y")

    lines(m[,1]+.5, m[,2]+.5)

    ## get rotation matrix
    R = rotmat2D(32)

    #########  apply rotation
    nm=m %*% R

    ###  plot
    lines(nm[,1]+.5, nm[,2]+.5, col='red')

[Package GEOmap version 2.4-0 Index]