concatenationLayer

Concatenation layer

Description

A concatenation layer takes inputs and concatenates them along a specified dimension. The inputs must have the same size in all dimensions except the concatenation dimension.

Specify the number of inputs to the layer when you create it. The inputs have the names 'in1','in2',...,'inN', where N is the number of inputs. Use the input names when connecting or disconnecting the layer by using connectLayers or disconnectLayers.

Creation

Syntax

layer = concatenationLayer(dim,numInputs)

layer = concatenationLayer(dim,numInputs,'Name',name)

Description

layer = concatenationLayer(dim,numInputs) creates a concatenation layer that concatenates numInputs inputs along the specified dimension, dim. This function also sets the Dim and NumInputs properties.

layer = concatenationLayer(dim,numInputs,'Name',name) also sets the Name property. To create a network containing a concatenation layer, you must specify a layer name.

Properties

Concatenation

Dim — Concatenation dimension

positive integer

Concatenation dimension, specified as a positive integer.

Example: 4

Layer

Name — Layer name

'' (default) | character vector | string scalar

Layer name, specified as a character vector or a string scalar. To include this layer in a layer graph, you must specify a layer name.

Data Types: char | string

NumInputs — Number of inputs

positive integer

Number of inputs to the layer, specified as a positive integer.

The inputs have the names 'in1','in2',...,'inN', where N equals NumInputs. For example, if NumInputs equals 3, then the inputs have the names 'in1','in2', and 'in3'. Use the input names when connecting or disconnecting the layer by using connectLayers or disconnectLayers.

InputNames — Input Names

{'in1','in2',…,'inN'} (default)

Input names, specified as {'in1','in2',...,'inN'}, where N is the number of inputs of the layer.

Data Types: cell

NumOutputs — Number of outputs

1 (default)

Number of outputs of the layer. This layer has a single output only.

Data Types: double

OutputNames — Output names

{'out'} (default)

Output names of the layer. This layer has a single output only.

Data Types: cell

Examples

Create and Connect Concatenation Layer

Create a concatenation layer that concatenates two inputs along the fourth dimension (channels). Name the concatenation layer 'concat'.

concat = concatenationLayer(4,2,'Name','concat')

concat = 
  ConcatenationLayer with properties:

          Name: 'concat'
           Dim: 4
     NumInputs: 2
    InputNames: {'in1'  'in2'}

Create two ReLU layers and connect them to the concatenation layer. The concatenation layer concatenates the outputs from the ReLU layers.

relu_1 = reluLayer('Name','relu_1');
relu_2 = reluLayer('Name','relu_2');

lgraph = layerGraph();
lgraph = addLayers(lgraph, relu_1);
lgraph = addLayers(lgraph, relu_2);
lgraph = addLayers(lgraph, concat);

lgraph = connectLayers(lgraph, 'relu_1', 'concat/in1');
lgraph = connectLayers(lgraph, 'relu_2', 'concat/in2');
plot(lgraph)