plotting of matlab function

Question

let us consider following picture

i wrote following code

>> t=-0.01:0.005:0.02;
>> y=cos(2*pi*100*t);
>> plot(t,y)

and got result

why it is so rough picture?also i have sampled it

>> t=0:Ts:0.02;
>> y=cos(2*pi*100*t);
>> plot(t,y)

i have got following picture

this seems ok,but about first one how can i make it more smooth?

Answer 1

You are plotting from -0.01 to 0.02 with a step of 0.005 , so that's only 7 data points. No wonder why your plot isn't smooth...

You need to refine your sampling by changing your 0.005 step to something much smaller. Start with 0.001 for example (that will give you 5 times more data points) and experiment until you are satisfied with the result:

t=-0.01:0.001:0.02;