This function checks whether an incomplete block design is orthogonal or not.
Incidence matrix of the design is to be supplied as input to the function. If the design is
orthogonal, it returns a value of 1 else it returns 0.
# NOT RUN {N=matrix(c(1,0,0,0,1,0,1,0,0,0,1,0,1,1,0,0,1,0,1,1,0,1,0,1,1,0,0,0,0,1,1,0,0,0,1,1,1,0,
0,0,1,0,0,1,0,1,1,0,0),nrow=7,byrow=TRUE)
is.orthogonal(N)
# }