How can I add additional minor grid lines?

VEL=[10,8,7,7,8,10,11,2,1,.1] t =[.2,.4,.6,.8,1,1.2,1.4,1.6,1.8,2] y=(VEL); x=(t); loglog(x,y,'-k'); ylabel('Psedo Velocity, m/s'); xlabel('Frequency, Hz'); grid on;

How can I add two minor gridlines running 45degrees and 135 degrees?? Please help.

[Rik]

If you only want specific line, I would suggest using plot. You can also look if XMinorTick or YMinorTick do what you need (together with XMinorGrid and YMinorGrid).