List of Deep Learning Layers

This page provides a list of deep learning layers in MATLAB^®.

To learn how to create networks from layers for different tasks, see the following examples.

Task	Learn More
Create deep learning networks for image classification or regression.	Create Simple Deep Learning Network for Classification Train Convolutional Neural Network for Regression Train Residual Network for Image Classification
Create deep learning networks for sequence and time series data.	Sequence Classification Using Deep Learning Time Series Forecasting Using Deep Learning
Create deep learning network for audio data.	Speech Command Recognition Using Deep Learning
Create deep learning network for text data.	Classify Text Data Using Deep Learning Generate Text Using Deep Learning

Layer Functions

Use the following functions to create different layer types. Alternatively, you can define your own custom layers. To learn how to define your own custom layers, see Define Custom Deep Learning Layers.

Input Layers

Function	Description
imageInputLayer	An image input layer inputs 2-D images to a network and applies data normalization.
image3dInputLayer	A 3-D image input layer inputs 3-D images or volumes to a network and applies data normalization.
sequenceInputLayer	A sequence input layer inputs sequence data to a network.
roiInputLayer (Computer Vision Toolbox™)	An ROI input layer inputs images to a Fast R-CNN object detection network.

Convolution and Fully Connected Layers

Function	Description
convolution2dLayer	A 2-D convolutional layer applies sliding convolutional filters to the input.
convolution3dLayer	A 3-D convolutional layer applies sliding cuboidal convolution filters to three-dimensional input.
groupedConvolution2dLayer	A 2-D grouped convolutional layer separates the input channels into groups and applies sliding convolutional filters. Use grouped convolutional layers for channel-wise separable (also known as depth-wise separable) convolution.
transposedConv2dLayer	A transposed 2-D convolution layer upsamples feature maps.
transposedConv3dLayer	A transposed 3-D convolution layer upsamples three-dimensional feature maps.
fullyConnectedLayer	A fully connected layer multiplies the input by a weight matrix and then adds a bias vector.

Sequence Layers

Function	Description
sequenceInputLayer	A sequence input layer inputs sequence data to a network.
lstmLayer	An LSTM layer learns long-term dependencies between time steps in time series and sequence data.
bilstmLayer	A bidirectional LSTM (BiLSTM) layer learns bidirectional long-term dependencies between time steps of time series or sequence data. These dependencies can be useful when you want the network to learn from the complete time series at each time step.
sequenceFoldingLayer	A sequence folding layer converts a batch of image sequences to a batch of images. Use a sequence folding layer to perform convolution operations on time steps of image sequences independently.
sequenceUnfoldingLayer	A sequence unfolding layer restores the sequence structure of the input data after sequence folding.
flattenLayer	A flatten layer collapses the spatial dimensions of the input into the channel dimension.
wordEmbeddingLayer (Text Analytics Toolbox™)	A word embedding layer maps word indices to vectors.

Activation Layers

Function	Description
reluLayer	A ReLU layer performs a threshold operation to each element of the input, where any value less than zero is set to zero.
leakyReluLayer	A leaky ReLU layer performs a threshold operation, where any input value less than zero is multiplied by a fixed scalar.
clippedReluLayer	A clipped ReLU layer performs a threshold operation, where any input value less than zero is set to zero and any value above the clipping ceiling is set to that clipping ceiling.
eluLayer	An ELU activation layer performs the identity operation on positive inputs and an exponential nonlinearity on negative inputs.
tanhLayer	A hyperbolic tangent (tanh) activation layer applies the tanh function on the layer inputs.
preluLayer (Custom layer example)	A PReLU layer performs a threshold operation, where for each channel, any input value less than zero is multiplied by a scalar learned at training time.

Normalization, Dropout, and Cropping Layers

Function	Description
batchNormalizationLayer	A batch normalization layer normalizes each input channel across a mini-batch. To speed up training of convolutional neural networks and reduce the sensitivity to network initialization, use batch normalization layers between convolutional layers and nonlinearities, such as ReLU layers.
crossChannelNormalizationLayer	A channel-wise local response (cross-channel) normalization layer carries out channel-wise normalization.
dropoutLayer	A dropout layer randomly sets input elements to zero with a given probability.
crop2dLayer (Computer Vision Toolbox)	A 2-D crop layer applies 2-D cropping to the input.

Pooling and Unpooling Layers

Function	Description
averagePooling2dLayer	An average pooling layer performs down-sampling by dividing the input into rectangular pooling regions and computing the average values of each region.
averagePooling3dLayer	A 3-D average pooling layer performs down-sampling by dividing three-dimensional input into cuboidal pooling regions and computing the average values of each region.
maxPooling2dLayer	A max pooling layer performs down-sampling by dividing the input into rectangular pooling regions, and computing the maximum of each region.
maxPooling3dLayer	A 3-D max pooling layer performs down-sampling by dividing three-dimensional input into cuboidal pooling regions, and computing the maximum of each region.
maxUnpooling2dLayer	A max unpooling layer unpools the output of a max pooling layer.

Combination Layers

Function	Description
additionLayer	An addition layer adds inputs from multiple neural network layers element-wise.
depthConcatenationLayer	A depth concatenation layer takes inputs that have the same height and width and concatenates them along the third dimension (the channel dimension).
concatenationLayer	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.
weightedAdditionLayer (Custom layer example)	A weighted addition layer scales and adds inputs from multiple neural network layers element-wise.

Object Detection Layers

Function	Description
roiInputLayer (Computer Vision Toolbox)	An ROI input layer inputs images to a Fast R-CNN object detection network.
roiMaxPooling2dLayer (Computer Vision Toolbox)	An ROI max pooling layer outputs fixed size feature maps for every rectangular ROI within the input feature map. Use this layer to create a Fast or Faster R-CNN object detection network.
regionProposalLayer (Computer Vision Toolbox)	A region proposal layer outputs bounding boxes around potential objects in an image as part of the region proposal network (RPN) within Faster R-CNN.
rpnSoftmaxLayer (Computer Vision Toolbox)	A region proposal network (RPN) softmax layer applies a softmax activation function to the input. Use this layer to create a Faster R-CNN object detection network.
rpnClassificationLayer (Computer Vision Toolbox)	A region proposal network (RPN) classification layer classifies image regions as either object or background by using a cross entropy loss function. Use this layer to create a Faster R-CNN object detection network.
rcnnBoxRegressionLayer (Computer Vision Toolbox)	A box regression layer refines bounding box locations by using a smooth L1 loss function. Use this layer to create a Fast or Faster R-CNN object detection network.

Output Layers

Function	Description
softmaxLayer	A softmax layer applies a softmax function to the input.
classificationLayer	A classification layer computes the cross entropy loss for multi-class classification problems with mutually exclusive classes.
regressionLayer	A regression layer computes the half-mean-squared-error loss for regression problems.
pixelClassificationLayer (Computer Vision Toolbox)	A pixel classification layer provides a categorical label for each image pixel or voxel.
rpnSoftmaxLayer (Computer Vision Toolbox)	A region proposal network (RPN) softmax layer applies a softmax activation function to the input. Use this layer to create a Faster R-CNN object detection network.
rpnClassificationLayer (Computer Vision Toolbox)	A region proposal network (RPN) classification layer classifies image regions as either object or background by using a cross entropy loss function. Use this layer to create a Faster R-CNN object detection network.
rcnnBoxRegressionLayer (Computer Vision Toolbox)	A box regression layer refines bounding box locations by using a smooth L1 loss function. Use this layer to create a Fast or Faster R-CNN object detection network.
weightedClassificationLayer (Custom layer example)	A weighted classification layer computes the weighted cross entropy loss for classification problems.
dicePixelClassificationLayer (Custom layer example)	A Dice pixel classification layer computes the Dice loss for semantic segmentation problems.
sseClassificationLayer (Custom layer example)	A classification SSE layer computes the sum of squares error loss for classification problems.
maeRegressionLayer (Custom layer example)	A regression MAE layer computes the mean absolute error loss for regression problems.