Helper function for plotting - returns breaks for image
plot function for object of class nifti
breaker(x, zlim, col, breaks = NULL)Vector of length 2
If breaks = NULL, then vector of length(col) + 1,
otherwise returns breaks
Object of class nifti
A user-specified zlim. If NULL, will calculate how
ortho2 would calculate zlim
colors to be plotted. Only used for length(col), so can be a
vector of length cols to be plotted
if !is.null(breaks), then will calculate breaks. Otherwise will
return this breaks vector