Hi
In the first week lecture we are introduced to nerual network and the digit recoginiton example. I have a basic question, how do we decide the number of layers and the number of units in each layer? for example in the example we hade 3 layers and different number of units in each of them. I want to learn how did we choose this number ? how did we diecide that we will have 3 layers, first one will have 25 units second will have 15 and so on …

I was thinking the same thing as Sourabh_Mishra. I just finished the course and the neural networks seem to be incredibly useful but there was never any general guidance of how to build the hidden layers and how many units to solve different types of problems. Is the 25 / 15, … a good place to start or are these only appropriate for certain types of models ?