I search the Caffe source code a bit, and the
ReadImageToDatum function in
caffe/src/caffe/util/io.cpp only supports
int type labels.
I've also noticed that there's an
array_to_datum function in
caffe/python/caffe/io.py, which seems to not have the constraint on the type of label, but I'm not exactly sure how I'm supposed to use it.
How can I use numerical (non-integers) labels for regression?
Datum type was designed with image classification in mind.
For regression, I recommend using
"HDF5Data" input layer.
See this answer for example.
Using hdf5 binary files allows for more flexibility in the number, shape and type of inputs you feed your net.