function s = e11v3(m)
% s = e11v3(m): return a $m$-by-$2m$ string matrix $s$ with
% + $*$s on the border (left, right, top, and bottom edges)
% + $\$s on the diagonal, except for on the border
%   (the *diagonal* of a matrix = all valid positions (i,i) in the matrix)
% + $-$s below the diagonal, except for on the border
% + $+$s on the boundary, $@$s in the interior, and $c$ at the center of
%   a disk of radius $round(m*.35)$ and center $(round(m*1.5),round(m/2))$

% version where $y$s are generated from $x$s

n = 2*m; % width of $s$             % [3/14] fixed typo below, where $xc<-->yc$
xc = round(m*1.5); yc = round(m/2); % (yc,xc) = center of disk
r = round(m*.35);                   % radius of disk

% note: deleted definition of coordinate matrices $x$,$y$ from skeleton code

s(m,n) = ' '; % make $s$ large enough
s(:,:) = 'o'; % fill each element with $'o'$

% place $-$s below diagonal: y > x
    for x = 1:n
        for y = x+1:m;
            s(y,x) = '-';
        end
    end

% place $\$s on diagonal: y = x
    for x = 1:n % or just $1:m$ and omit the conditional test below
        if x <= m
            y = x;
            s(y,x) = '\';
        end
    end
    

% place $*$s on border: x = 1, x = n, y = 1, y = m
    % left edge
        x = 1;
        for y = 0*x + (1:m) % or just $1:m$
            s(y,x) = '*';
        end
    % right edge
        x = n;
        for y = 0*x + (1:m) % or just $1:m$
            s(y,x) = '*';
        end
    % top and bottom edges
        for x = 1:n
            % top edge
                y = 0*x + 1; % or just $1$
                s(y,x) = '*';
            % bottom edge
                y = 0*x + m; % or just $m$
                s(y,x) = '*';
        end

warning('disk not done using this approach')