Residual Variance (Euclidean and Tangent Distances)
Dimensionality: 3-4 The Variance doesn't decrease much beyong the knee at 3.
This dimensionality may be attributed to 3 DOF of Nao's arm: 1 at the elbow and 2 at the shoulders.
Residual Variance (Euclidean and Tangent Distances)
Dimensionality: 4 The Residual Variance doesn't decrease much beyond the knee at 4th dimensionality.
This may be attributed to four angles which uniquely determine an image of this set.
3D plot with images(Euclidean and Tangent Distances)
While the Euclidean plot reveals a correspondance between coordinates and the arms' configurations,
the Tangent plot doesn't help so much (tangent algo fails here due to uniform shades of black, blue and red).
Dimensionality: 1 Although it appears from the Euclidean plot that dimensionality is 5 (the knee of the graph), but a deeper analysis shows that variance drops only by 0.009 from 1st to 5th dimensionality. Since the mere position of box determines all the four angles of the arms, the dimension reduces to two. Since the box moves only horizontally, the dimension further falls down to 1.