[R] how to rotate a triangle image(ZMAT) ?

[Cleber N.Borges]

I thank François Pinard for your attention

one solution, but
very dirty
very ugly
and ~ 30% of calculations cut loose!

if somebody can give a tip, I thank...

Cleber

############
 f <- function(x,y){
 z=1-x-y
 z[ z < (-1e-15) ] <- NA 
 return( -100*x + 0*y + 100*z )
 }

 x = y = seq( 1, 0, by = -0.01 )
 z =  outer(x,y,f)
 
 t1 = length(x)
 aux = numeric(0)
 im  = numeric(0)
 for( i in seq( 1, t1, by = 2 ) ){
    idx = seq( i*t1, t1**2, by = t1 ) - (0:(t1 - i))
    im = c(im, aux, z[idx], aux )
    aux = c(aux, NA)
 }
 im = matrix(im,nr=t1)

 image(im,  col=terrain.colors(256))
 contour(im, add=T)