function scaling = addvec(resultant,varargin)
% graphical interface for adding vectors.
% RATHER THAN CHANGING Vone and Vtwo, change the scale factor.
% switch to a matrix formulation so you can index the various vectors
% ad add as many as you want.
% Add a solve key
% Add more vectors
% add a key to add a small random component to each vector

mat = []; redraw=1;
try
    for k=1:length(varargin)
        foo = varargin{k};
        mat = [mat, foo(:)];
    end
catch
    error('Vectors must all be the same length');
end

[dimension,nvecs] = size(mat);
scaling = ones(nvecs,1);

activewidth=8; normalwidth=3; activevec=1;
scalefactor = 1.5;
plotrangex = max( resultant(1), max(cumsum(abs(mat(1,:)))));
plotrangey = max( resultant(2), max(cumsum(abs(mat(2,:)))));
if dimension == 3
    plotrangez = max( resultant(3), max(cumsum(abs(mat(3,:)))));
end

ff = figure(1); clf;
set(ff,'WindowButtonDownFcn', 'rotate3d(''down'')');
set(ff,'WindowButtonUpFcn', 'rotate3d(''up'')');

if dimension == 3
    plot3([0 1], [0,1],[0,1]);
    grid on;
end
set(gca,'xlim', scalefactor*plotrangex*[-1,1], 'ylim', scalefactor*plotrangey*[-1,1]);
if dimension == 3
    set(gca, 'zlim', scalefactor*plotrangey*[-1,1]);
end

if dimension == 3
    plotrangez = max( resultant(1), max(cumsum(abs(mat(3,:)))));
    set(gca, 'zlim', scalefactor*plotrangez*[-1,1]);
end
coords = 1:dimension;

noextension = 0;
vectorlines = makelines(resultant,mat,scaling,...
    coords, activevec, normalwidth, activewidth,noextension);
drawlines(vectorlines, resultant,mat,scaling,...
    coords, activevec, normalwidth, activewidth,noextension);



while 1 
    w = waitforbuttonpress;
    if w == 1
        k = get(gcf,'CurrentChar');
        switch k
        case 'c' % change camera position
            set(gca,'CameraPosition', mat(:,activevec));
        case 'f' % flip the sign of the active vector
            scaling(activevec) = -scaling(activevec);
            redraw = 1;
        case {'b','s'} % enlarge or shrink the axes
            if k=='b'
                scalefactor = 1.5*scalefactor;
            else
                scalefactor = .66*scalefactor;
            end
            set(gca, 'xlim', scalefactor*plotrangex*[-1,1], ...
                'ylim', scalefactor*plotrangey*[-1,1]);
            if dimension == 3
                set(gca, 'zlim', scalefactor*plotrangez*[-1,1]);
            end
            redraw = 1;
        case 'e'
            noextension = ~ noextension;
            redraw = 1;
        case {29,'='} % grow the vector
            scaling(activevec) = 1.05*scaling(activevec);
            redraw = 1;
        case {28, '-'} % shrink the vector
            scaling(activevec) = 0.95*scaling(activevec);
            redraw = 1;
        case 'x'
            % print out the solution so far
            disp(scaling);
        case 'n' % move to the next vector
            activevec = activevec+1;
            if activevec > nvecs
                activevec = 1;
            end
            redraw = 1;
        case 'm' % move to the previous vector
            activevec = activevec - 1;
            if activevec <= 0
                activevec = nvecs;
            end
            redraw=1;
        case 'r' % prepare for rotation
            rotate3d on;
        case {'q',27}
            break;
        end
    else
        %mouse click    
    end
    if redraw
        redraw = 0;
    drawlines(vectorlines, resultant,mat,scaling,...
        coords, activevec, normalwidth, activewidth,noextension);

    end
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function res = makelines(resultant, mat, scaling, coords,activevec,normalwidth,activewidth,noextension)

shadowgray = [.8,.8,.8];
[dimension,nvecs] = size(mat);
mymat = mat(coords,:).*kron(scaling(:)',ones(dimension,1));

colors = 'bgmckbgmckbgmckbgmckbgmckbgmck'; 
colors = [colors, colors, colors, colors];

if length(coords) == 2
    res.resultant = line( [resultant(coords(1))],[resultant(coords(2))]);
else % 3 -dimensional
    res.resultant = line(resultant(coords(1)), resultant(coords(2)), ...
        resultant(coords(3)));
    res.resultantxy = line(resultant(coords(1)), resultant(coords(2)), ...
        resultant(coords(3)), 'Marker', 'diamond', ...
        'markersize', 10, 'MarkerFaceColor', shadowgray, 'EraseMode','xor');
    res.resultantyz = line(resultant(coords(1)), resultant(coords(2)), ...
        resultant(coords(3)),'Marker', 'diamond', ...
        'markersize', 10, 'MarkerFaceColor', shadowgray, 'EraseMode','xor');
    res.resultantxz = line(resultant(coords(1)), resultant(coords(2)), ...
        resultant(coords(3)), 'Marker', 'diamond', ...
        'markersize', 10, 'MarkerFaceColor', shadowgray, 'EraseMode','xor');
end
set(res.resultant, 'Color', 'r', 'Marker', 'diamond', ...
        'markersize', 10, 'MarkerFaceColor', 'r', 'EraseMode','xor');
heads = cumsum(mymat,2);
tails = cumsum( [zeros(dimension,1), mat(:,1:end-1)],2);
big = 100;
for k=1:nvecs
    xpts = [heads(coords(1),k), tails(coords(1),k)];
    ypts = [heads(coords(2),k), tails(coords(2),k)];
    if length(coords) == 2
        res(k).vec = line(xpts, ypts, 'color',colors(k), ...
            'linewidth', normalwidth, 'EraseMode', 'Xor');
    else
        zpts = [heads(coords(3),k), tails(coords(3),k)];
        res(k).vec = line(xpts, ypts, zpts, 'color', colors(k), ...
            'linewidth', normalwidth, 'EraseMode', 'Xor');
        res(k).shadowxy = line(xpts,ypts,[0 0], 'color', shadowgray, ...
            'linewidth', normalwidth, 'EraseMode', 'Xor');
        res(k).shadowxz = line(xpts, [0,0], zpts, 'color', shadowgray, ...
            'linewidth', normalwidth, 'EraseMode', 'Xor');
        res(k).shadowyz = line([0,0], ypts, zpts, 'color', shadowgray, ...
            'linewidth', normalwidth, 'EraseMode', 'Xor');
    end
    extxpts = [heads(coords(1),k) + big*mat(coords(1),k)*[-1,1]];
    extypts = [heads(coords(2),k) + big*mat(coords(2),k)*[-1,1]];
    if length(coords == 2)
        res(k).ext = line(extxpts,extypts,'color',colors(k), ...
            'LineStyle', ':', 'EraseMode', 'Xor');
    else
        extzpts = [heads(coords(3),k) + big*mat(coords(3),k)*[-1,1]];
        res(k).ext = line(extxpts,extypts,extzpts, 'color',colors(k), ...
            'LineStyle', ':', 'EraseMode', 'Xor');
    end
end
set(res(activevec).vec, 'LineWidth', activewidth);
return

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function drawlines(res, resultant, mat, scaling, coords,activevec,normalwidth,activewidth,noextension)

[dimension,nvecs] = size(mat);
dimension = length(coords);
mymat = mat(coords,:).*kron(scaling(:)',ones(dimension,1));

colors = 'bgmckbgmckbgmckbgmckbgmckbgmck'; 
colors = [colors, colors, colors, colors];

%set(res(1).resultant, 'Xdata', [resultant(coords(1))], ...
%    'Ydata', [resultant(coords(2))], ...
%    'Color', 'r', 'linewidth', normalwidth);
heads = cumsum(mymat,2);
tails = cumsum( [zeros(dimension,1), mymat(:,1:end-1)],2);
big = 100;
for k=1:nvecs
    xpts = [heads(coords(1),k), tails(coords(1),k)];
    ypts = [heads(coords(2),k), tails(coords(2),k)];
    set(res(k).vec, 'Xdata', xpts, 'Ydata', ypts, 'LineWidth', normalwidth)
    if dimension == 3
        zpts = [heads(coords(3),k), tails(coords(3),k)];
        set(res(k).vec, 'Zdata', zpts);
        zplane = min(get(gca, 'Zlim'));
        yplane = max(get(gca, 'Ylim'));
        xplane = max(get(gca,'Xlim'));
        set(res(k).shadowxy, 'Xdata', xpts, 'Ydata', ypts,...
            'Zdata', zplane.*[1,1], ...
            'LineWidth', normalwidth);
        set(res(k).shadowxz, 'Xdata', xpts, ...
            'Ydata', yplane.*[1,1], ...
            'Zdata', zpts, 'LineWidth', normalwidth);
        set(res(k).shadowyz, 'Xdata', xplane.*[1,1], ...
            'Ydata', ypts, ...
            'Zdata', zpts, 'LineWidth', normalwidth); 
        if k==1
            set(res(1).resultantxy, 'Zdata', zplane);
            set(res(1).resultantxz, 'Ydata', yplane);
            set(res(1).resultantyz, 'Xdata', xplane);
        end
    end
    
    extxpts = [tails(coords(1),k) + big*mat(coords(1),k)*[-1,1]];
    extypts = [tails(coords(2),k) + big*mat(coords(2),k)*[-1,1]];
    set(res(k).ext, 'Xdata', extxpts, 'Ydata', extypts);
    if noextension
        set(res(k).ext, 'Color', [1 1 1]);
    else
        set(res(k).ext, 'Color', colors(k));
    end
    
    if dimension == 3
       extzpts = [tails(coords(3),k) + big*mat(coords(3),k)*[-1,1]]; 
       set(res(k).ext, 'Zdata', extzpts);
       
   end
end
set(res(activevec).vec, 'LineWidth', activewidth);

return