I need to plot and save to image file in MATLAB. Here is the code that I am calling inside a 'for' loop: 

figure
scatter(data_x_pos,data_y_pos,'r*')
hold on
scatter(data_x_neg,data_y_neg,'b')
t = linspace(-80,80);
y = -model.w(1)*t/model.w(2);
plot(t,y,'k');
% need to save this plot to image to a file here 

Now, this is starter code that I am using for some work and I don't understand it completely (example - the command 'figure'). There have been suggestions to use saveas or print but I believe I need handles for them. Could someone help me out here? 

Answers: 

figure() is a function which returns a handle to the figure: 

 f = figure()
scatter(data_x_pos,data_y_pos,'r*')

... 
You can then use this handle to save the figure: 

saveas(f, 'image.png'); 

Take a look at the tutorials on Handle Graphics to learn more.

scatter, and plot also return handles to the collection of points, or the lines, or whatever, they've plotted.