with learned features h 1 = f FP,θFP (x FP ) and h 2 = f FG,θFG (x FG ), where x FP represents the fingerprint part of the IR spectrum, x FG represents the functional group part of the IR spectrum, and θ joint , θ FP , θ FG being the weights of the three neural networks f joint , f FP , and f FG in the overall architecture.