MATLAB: Shift plot indexing

plotshifttime

I want to plot, for example, population sizes versus time, with t=0 being the first point. How do I get something like

A = [10 9 7 8 4 2 5 1 0;
    10 12 6 8 3 3 4 2 0];
plot(A');

to have the x-axis go from 0 to 8 instead of 1 to 9 (i.e., shift the entire plot to the left 1 unit)?

A = [10 9 7 8 4 2 5 1 0;
    10 12 6 8 3 3 4 2 0];
plot(0:size(A,2)-1,A');

Start with "If an entry in B is greater than or equal to zero": You can either run a loop over all elements of B or use "logical indexing":

% Linear indexing:
for k = 1:numel(B)
   if B(k) >= 0
     ...
   end
end

Or two indices for rows and columns:

for r = 1:size(B, 2)
  for c = 1:size(B, 1)
    if B(r, c) >= 0
       ...
    end
  end
end

Or "logical indexing":

index = (B >= 0);
disp(B(index))

Now try to use this to modify B. Use the mentioned terms to search in the documentation and in the internet.