Trouble with figure output in matlab -

i try figure large data file (about 400 mb) using matlab 2010b on windows 7 x64 ultimate. here code

function psi12 op = load ('20_01_w=0-021_op_ksi1.txt');  z=op; tt=length(z); x=linspace(0,20,41); t=linspace(0,0.01*tt,tt); contourf(x,t,z) xlabel('x','fontsize',24) ylabel('t','fontsize',24) title(['v = 0.1, \omega = 0.021'],'fontsize',20) 

but after launch code first obtain figure white background. , after long waiting (about 3-4 hours) have desired contour plot. further editing of figure practically impossible, because long response commands in figure menu observed. it's interesting larger data files (about 900 mb or 1 gb) contour plot faster (within 10-15 minutes) , can edit figure without problems response figure menu.

do know solution of problem?

beside dan suggested, thing should load data directly z:

z = load ('20_01_w=0-021_op_ksi1.txt');