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(Not recommended) Directed acyclic graph (DAG) network for deep learning

DAGNetwork objects are not recommended. Use dlnetwork objects instead. For more information, see Version History.


A DAG network is a neural network for deep learning with layers arranged as a directed acyclic graph. A DAG network can have a more complex architecture in which layers have inputs from multiple layers and outputs to multiple layers.


There are several ways to create a DAGNetwork object:


To learn about other pretrained networks, see Pretrained Deep Neural Networks.


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This property is read-only.

Network layers, specified as a Layer array.

This property is read-only.

Layer connections, specified as a table with two columns.

Each table row represents a connection in the layer graph. The first column, Source, specifies the source of each connection. The second column, Destination, specifies the destination of each connection. The connection sources and destinations are either layer names or have the form "layerName/IOName", where "IOName" is the name of the layer input or output.

Data Types: table

This property is read-only.

Names of the input layers, specified as a cell array of character vectors.

Data Types: cell

This property is read-only.

Names of the output layers, specified as a cell array of character vectors.

Data Types: cell

Object Functions

activations(Not recommended) Compute deep learning network layer activations
classify(Not recommended) Classify data using trained deep learning neural network
predict(Not recommended) Predict responses using trained deep learning neural network
plotPlot neural network architecture
predictAndUpdateState(Not recommended) Predict responses using a trained recurrent neural network and update the network state
classifyAndUpdateState(Not recommended) Classify data using a trained recurrent neural network and update the network state
resetStateReset state parameters of neural network


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Create a simple directed acyclic graph (DAG) network for deep learning.

Train the network to classify images of digits. The simple network in this example consists of:

  • A main branch with layers connected sequentially.

  • A shortcut connection containing a single 1-by-1 convolutional layer. Shortcut connections enable the parameter gradients to flow more easily from the output layer to the earlier layers of the network.

Create the main branch of the network as a layer array. The addition layer sums multiple inputs element-wise. Specify the number of inputs for the addition layer to sum. To easily add connections later, specify names for the first ReLU layer and the addition layer.

layers = [
    imageInputLayer([28 28 1])

Create a layer graph from the layer array. layerGraph connects all the layers in layers sequentially. Plot the layer graph.

lgraph = layerGraph(layers);

Figure contains an axes object. The axes object contains an object of type graphplot.

Create the 1-by-1 convolutional layer and add it to the layer graph. Specify the number of convolutional filters and the stride so that the activation size matches the activation size of the third ReLU layer. This arrangement enables the addition layer to add the outputs of the third ReLU layer and the 1-by-1 convolutional layer. To check that the layer is in the graph, plot the layer graph.

skipConv = convolution2dLayer(1,32,'Stride',2,'Name','skipConv');
lgraph = addLayers(lgraph,skipConv);

Figure contains an axes object. The axes object contains an object of type graphplot.

Create the shortcut connection from the 'relu_1' layer to the 'add' layer. Because you specified two as the number of inputs to the addition layer when you created it, the layer has two inputs named 'in1' and 'in2'. The third ReLU layer is already connected to the 'in1' input. Connect the 'relu_1' layer to the 'skipConv' layer and the 'skipConv' layer to the 'in2' input of the 'add' layer. The addition layer now sums the outputs of the third ReLU layer and the 'skipConv' layer. To check that the layers are connected correctly, plot the layer graph.

lgraph = connectLayers(lgraph,'relu_1','skipConv');
lgraph = connectLayers(lgraph,'skipConv','add/in2');

Figure contains an axes object. The axes object contains an object of type graphplot.

Load the training and validation data, which consists of 28-by-28 grayscale images of digits.

[XTrain,YTrain] = digitTrain4DArrayData;
[XValidation,YValidation] = digitTest4DArrayData;

Specify training options and train the network. trainNetwork validates the network using the validation data every ValidationFrequency iterations.

options = trainingOptions('sgdm', ...
    'MaxEpochs',8, ...
    'Shuffle','every-epoch', ...
    'ValidationData',{XValidation,YValidation}, ...
    'ValidationFrequency',30, ...
    'Verbose',false, ...
net = trainNetwork(XTrain,YTrain,lgraph,options);

Figure Training Progress (28-Oct-2023 04:07:53) contains 2 axes objects and another object of type uigridlayout. Axes object 1 with xlabel Iteration, ylabel Loss contains 15 objects of type patch, text, line. Axes object 2 with xlabel Iteration, ylabel Accuracy (%) contains 15 objects of type patch, text, line.

Display the properties of the trained network. The network is a DAGNetwork object.

net = 
  DAGNetwork with properties:

         Layers: [16x1 nnet.cnn.layer.Layer]
    Connections: [16x2 table]
     InputNames: {'imageinput'}
    OutputNames: {'classoutput'}

Classify the validation images and calculate the accuracy. The network is very accurate.

YPredicted = classify(net,XValidation);
accuracy = mean(YPredicted == YValidation)
accuracy = 0.9932

Extended Capabilities

Version History

Introduced in R2017b

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R2024a: Not recommended

Starting in R2024a, DAGNetwork objects are not recommended, use dlnetwork objects instead.

There are no plans to remove support for DAGNetwork objects. However, dlnetwork objects have these advantages and are recommended instead:

  • dlnetwork objects are a unified data type that supports network building, prediction, built-in training, visualization, compression, verification, and custom training loops.

  • dlnetwork objects support a wider range of network architectures that you can create or import from external platforms.

  • The trainnet function supports dlnetwork objects, which enables you to easily specify loss functions. You can select from built-in loss functions or specify a custom loss function.

  • Training and prediction with dlnetwork objects is typically faster than LayerGraph and trainNetwork workflows.

To convert a trained DAGNetwork object to a dlnetwork object, use the dag2dlnetwork function.

This table shows some typical usages of DAGNetwork objects and how to update your code to use dlnetwork object functions instead.

Not RecommendedRecommended
Y = predict(net,X);
Y = minibatchpredict(net,X);
Y = classify(net,X);
scores = minibatchpredict(net,X);
Y = scores2label(scores,classNames);
Y = activations(net,X,layerName);
Y = predict(net,X,Outputs=layerName);
[net,Y] = predictAndUpdateState(net,X);
[Y,state] = predict(net,X);
net.State = state;
[net,Y] = classifyAndUpdateState(net,X);
[scores,state] = predict(net,X);
Y = scores2label(scores,classNames);
net.State = state;