Can I create function that use default input unless a user gives one?

Hi I want to create function that will use current time to calculate the position of satellites. But later on I will need this function to calculate the satellite position at a few second ahead of the current time for example current time is let's say 50 seconds for the sake of simplicity and I want to update it with 2 second later.

Now I want this function to calculate the sat position at t = 50 seconds by defult unless I give it the 2 second and it adds to the first time. Please check the code structure for better understanding of the uestion

function satposit(time)
    if nargin<0 
        t = 50 % just an example only 
        s = vt % just an example only 
    else if nargin>=1 
        t = 50 + time
        s = vt 
    end

end

Answer 1

[Rik]

The code you show is almost exactly what you describe (except for the <0 instead of <1): if the user doesn't provide an input, it will set t to 50, otherwise it will set t to 50+time.

You could have found this error using the debugger to step through your code.

Note that this is a more common way to do this:

function satposit(time)
if nargin<1
    time=0; % define the default value of time
end
t = 50 + time;
s = vt;
end