How do I plot data in Octave?

I wanted to plot a data in Octave for a logistic regression problem my teacher in my university assigned me to solve.
Let’s say the input-training features is a matrix X and output is y=1 or y=0
To plot the data I made this statement:

pos = find(y==1);neg = find(y==0);

plot(X(pos,1),X(pos,2),’k+’,’LineWidth’,2,’MarkerSize’,7);

plot(X(neg,1),X(neg,2),’ko’,’MarkerFaceColor’,y,’MarkerSize’,7);

But it does not compile and it shows the single quotes as unidentified characters.
Please help…