truncate=function(b){
  b[b<0]=0
  b[b>1]=1
  return(b)
}

plot.image = function(b) { ## crtanje slike dimenzija 50x50 s vrijednostima piksela unutar [0,1]
  m = matrix(b,nrow=50, ncol=50)
  truncate(m) 
  image(m,col=gray.colors(30),zlim=c(0,1))
}


load("bstar.Rdata")
plot.image(bstar) ## bstar sadrzi samo 0 i 1
mean(bstar == 0) ## cak 83.36% nula ("sparse matrix")

p = length(bstar)
set.seed()  ### stavi neki broj
n = 1300 
## generiranje podataka u njd slucaju
x = matrix(rnorm(n*p),nrow=n)
y = x%*%bstar + rnorm(n,sd=5)