Graphviz script to draw a multi-class neural network diagram. Copy this to a `file.txt` file and then run `dot -Tpng -O file.txt` from command-line to get a .png figure with the diagram.

multi_class_neural_netwrok_diagram

digraph G {

        rankdir=LR
	splines=line
        nodesep=.05;
        
        node [label=""];
        
        subgraph cluster_0 {
		color=white;
                node [style=solid,color=blue4, shape=circle];
		x1 x2 x3;
		label = "layer 1";
	}

	subgraph cluster_1 {
		color=white;
		node [style=solid,color=red2, shape=circle];
		a12 a22 a32 a42 a52;
		label = "layer 2";
	}

	subgraph cluster_2 {
		color=white;
		node [style=solid,color=red2, shape=circle];
		a13 a23 a33 a43 a53;
		label = "layer 3";
	}

	subgraph cluster_3 {
		color=white;
		node [style=solid,color=seagreen2, shape=circle];
		O1 O2 O3 O4;
		label="layer 4";
	}

        x1 -> a12;
        x1 -> a22;
        x1 -> a32;
        x1 -> a42;
        x1 -> a52;

        x2 -> a12;
        x2 -> a22;
        x2 -> a32;
        x2 -> a42;
        x2 -> a52;
 
        x3 -> a12;
        x3 -> a22;
        x3 -> a32;
        x3 -> a42;
        x3 -> a52;

        a12 -> a13
        a22 -> a13
        a32 -> a13
        a42 -> a13
        a52 -> a13

        a12 -> a23
        a22 -> a23
        a32 -> a23
        a42 -> a23
        a52 -> a23

        a12 -> a33
        a22 -> a33
        a32 -> a33
        a42 -> a33
        a52 -> a33

        a12 -> a43
        a22 -> a43
        a32 -> a43
        a42 -> a43
        a52 -> a43

        a12 -> a53
        a22 -> a53
        a32 -> a53
        a42 -> a53
        a52 -> a53

        a13 -> O1
        a23 -> O1
        a33 -> O1
        a43 -> O1
        a53 -> O1

        a13 -> O2
        a23 -> O2
        a33 -> O2
        a43 -> O2
        a53 -> O2

        a13 -> O3
        a23 -> O3
        a33 -> O3
        a43 -> O3
        a53 -> O3

        a13 -> O4
        a23 -> O4
        a33 -> O4
        a43 -> O4
        a53 -> O4



}

nice, thanks a lot

You can use this to simplify:

{ x1 x2 x3 } -> { a12 a22 a32 a42 a52 }
             -> { a13 a23 a33 a43 a53 }
             -> { O1 O2 O3 O4 }