function y= histogram(x)
z1=max(x)
z2=min(x)
ninterval=15;
interval=(z1-z2)/ninterval;
for i=1:ninterval+1
    y(1,i)=z2+(i-1)*interval;
    y(2,i)=zeros;
end
length(x)

for i=1:length(x)
    j=floor((x(i)-z2)/interval)+1;
    y(2,j)=y(2,j)+1;
end
y(2,:)=y(2,:)/length(x);