From next time, please post the code you tried and where you have struck. So, that if one wants to try out the things, it helps to provide proper answer. Though you ask for plot of it, you haven't shown what is tried to plot for it.
I did take some possible values and tried to code what you are looking for.
A = 0.5;
F = 1000;
T = 0:1/(20*F):2/F;
Phase = 0;
DC_Voltage = ((A) * sin((2)*(pi*F).*(T)+(Phase)));
DC_Voltage_Negative_Idx = DC_Voltage < 0;
DC_Voltage(DC_Voltage_Negative_Idx) = 0;
Hope this helps.