Output argument y issue

x=sequence([1 2 3 4 5],-1);

stem(flip(shift(x,2)))

when I enter this on the command window, it says the Output argument "y" (and maybe others) not assigned during call to "sequence/shift".

what did i do wrong?

classdef sequence
	properties
		data
		offset
	end
	
	methods
		function s = sequence(data, offset)
			% SEQUENCE   Sequence object
			%            S = SEQUENCE(DATA, OFFSET) creates sequence S
			%            using DATA and OFFSET
			%
			%            Your Name  1 Jan 2014
			s.data = data;
			s.offset = offset;
		end
		
		function display(s)
			var = inputname(1);
			if (isempty(var))
				disp('ans =');
			else
				disp([var '=']);
			end
			switch length(s.data)
				case 0
					disp('    data: []')
				case 1
					disp(['    data: ', num2str(s.data)])
				otherwise
					disp(['    data: [' num2str(s.data) ']'])
			end
			disp(['  offset: ' num2str(s.offset)])
		end
		
		function y = flip(x)
			% FLIP Flip a Matlab sequence structure, x, so y = x[-n]
           
            y=fliplr(x);
            
		end
		
		function y = shift(x, n0)
			% SHIFT Shift a Matlab sequence structure, x, by integer amount n0 so that y[n] = x[n - n0]
		for i=1:numel(x)
      
                if(i-n0)>0
                    y(i)=x(i-n0);
                    
                end
            end
        end
		
		function z = plus(x, y)
			% PLUS  Add x and y. Either x and y will both be sequence structures, or one of them may be a number.
		z=x+y;
        end
		
		function z = minus(x, y)
			% MINUS Subtract x and y. Either x and y will both be sequence structures, or one of them may be a number.
		z=x-y;
        end
		
		function z = times(x, y)
			% TIMES Multiply x and y (i.e. .*) Either x and y will both be sequence structures, or one of them may be a number.
		z=x.*y;
        end
		
		function stem(x)
			% STEM Display a Matlab sequence, x, using a stem plot.
		figure 
        steam(x)
        end
	end
end

Answer 1

[Walter Roberson]

Your methods are not static. Input to shift is a sequence object, which you need to extract the data property of.

[xoxox]

can you show me the correct way?

[Walter Roberson]

What does the offset component of the sequence mean? If it means what I suspect it means, then why is it that shift() does not just return a sequence with the same data and a different shift?

I suspect that you intend that object represents a chunk of data at an offset into a vector. If so then is the beginning of the vector offset 0 or offset 1? Is flip() intended to flip the data portion only leaving it at the same offset, or is flip() intended to (generally) change the position as well? For example should flip of _ 1 2 3 _ _ _ _ _ _ be _ 3 2 1 _ _ _ _ _ _ or should it be _ _ _ _ _ _ 3 2 1 _ ? If it is intended to be relative to the entire sequence then each sequence object also needs information about the length of the sequence.

Is the intention that any unfilled locations are 0?

Could you confirm that the intended plus() of sequence([1 2 3],2) and sequence([3 4 5],3) would be like _ 1 2 3 _ _ _ _ _ _ + _ _ 4 5 6 _ _ _ _ _ = _ 1 6 8 7 _ _ _ _ _ = sequence([1 6 8 7], 2) ?

What happens if you shift() data into negative offsets?