using Colors, LinearAlgebra, Plots, Statistics

function eigenfaces_scatter(images, indices)

    (w, h, nExpressions, nIndividuals) = size(images)
    X= reshape(images, (w*h, nIndividuals*nExpressions))
    avg = mean(X, dims=2)
    Xd = X .- avg
    (U,S,V) = svd(Xd)
    scores = U[:,indices]' * Xd
    # normalize scores and samples
    # scores = bsxfun(@rdivide,scores,sqrt(sum(abs(scores).^2)));

    if length(indices) == 3
        scatter(
            scores[1,:],
            scores[2,:],
            scores[3,:],
            markersize = 3*ones(size(scores[1,:])),
            marker_z = reshape(kron(1:nExpressions, ones(1,nIndividuals)'), (nExpressions*nIndividuals, 1)),
            legend = nothing
        )
    elseif length(indices) == 2
        scatter(
            scores[1,:],
            scores[2,:],
            markersize = 3*ones(size(scores[1,:])),
            marker_z = reshape(kron(1:nExpressions, ones(1,nIndividuals)'), (nExpressions*nIndividuals, 1)),
            legend = nothing
        )
    end
end