clf

% Initialization of needed quantities:
N = [3,5,7,15];
grid = linspace(-1/4,1/4,1000);
onefigure = 1;  % Plotting in one or two figures.

% Use the sinusoidal form to ascertain that the returned 
% values are real:
D = @(N,x) sin(2*pi*(2*N+1/2).*x)./sin(pi*x);

% Plotting:
if (onefigure == 0)
    plot(grid,D(N(1),grid),grid,D(N(3),grid));
    legend('N=3','N=7'); xlabel('x'); ylabel('D_N(x)');
    
    figure
    plot(grid,D(N(2),grid),grid,D(N(4),grid));
    legend('N=5','N=15'); xlabel('x'); ylabel('D_N(x)');
else
    plot(grid,D(N(1),grid),grid,D(N(2),grid),...
        grid,D(N(3),grid),grid,D(N(4),grid));
    legend('N=3','N=5','N=7','N=15'); xlabel('x');
    ylabel('D_N(x)');
end