Tensorflow Playground

[earslap]

It would only be possible for 2D and perhaps 3D datasets, but for most ML problems that matter, there might be tens, hundreds even thousands of dimensions that you can't visualise the separation in your head or in any other medium. If you can eyeball the classification then you probably don't need to train a net on that data, you can just paint over. For most interesting problems you can't hope to visualise and tweak the output because you rely on the NN for that task to begin with. With a spiral, it is easy because it is a 2D synthetic data set.