Flip a matrix to be passed to image.

Flip a matrix such that it will appear `as is' when plotted by image. Note that image shows the rows of the matrix on the x axis and the columns of the matrix on the y axis (with column 1 at the bottom), such that the matrix gets displayed rotated 90 degree clockwise. `flip4image' therefore rotates the matrix 90 degree coutner-clockwise, such that the rotation made by image results in the desired form of the matrix.

flip4image(x)

Arguments

x	a matrix

Value

The matrix x prepared to be displyed by image.

Examples

# plot a toy matrix
m<-rbind(1:10,c(1:3,14:20),20*sin(seq(0,4*pi,length=10)))
m
#>      [,1]     [,2]     [,3]      [,4]      [,5]     [,6]     [,7]      [,8]
#> [1,]    1  2.00000 3.000000   4.00000   5.00000  6.00000  7.00000  8.000000
#> [2,]    1  2.00000 3.000000  14.00000  15.00000 16.00000 17.00000 18.000000
#> [3,]    0 19.69616 6.840403 -17.32051 -12.85575 12.85575 17.32051 -6.840403
#>           [,9]         [,10]
#> [1,]   9.00000  1.000000e+01
#> [2,]  19.00000  2.000000e+01
#> [3,] -19.69616 -9.797174e-15
image(flip4image(m),col=gray.colors(20))
# with labels
image(x=1:10,y=1:3,z=flip4image(m),col=gray.colors(20),yaxt='n')
axis(2,at=1:3,labels=rev(1:3))

# plot a covariance matrix
m<-cov(matrix(rnorm(100),10,10))
image(flip4image(m),col=gray.colors(20))
# plot the Cholsky decomposition of the a covariance matrix (an upper triangular matrix)
image(flip4image(chol(cov(m))),col=gray.colors(20))