Unable to use a value of type DAGNetwork as an index.

I have build the UNET model, the training was interrupted,Now I am trying to resume the training from the last checkpoint, but i got the Error "Unable to use a value of type DAGNetwork as an index."

Here is my code, can someone tell me why i got this error.

clear all

close all

load('net_checkpoint__226644__2021_07_08__16_18_25.mat','net')

matlabpath = 'E:\My project';

data = fullfile(matlabpath,'ImageDatasetforPixelLabelDataSeries6-21');

data1 = fullfile(matlabpath,'PixelLabelDataSeries6-21');

imds = imageDatastore(data,'IncludeSubfolders',true,'LabelSource','foldernames');

classes = ["CatheterMarkerVessel" "Background"];

pixelLabelIDs = [0 1];

pxds = pixelLabelDatastore(data1, classes ,pixelLabelIDs);

trainingdata = pixelLabelImageSource(imds,pxds);

tbl = countEachLabel(trainingdata);

imageSize = [1024 1024 1];

numClasses = numel(classes);

lgraph = unetLayers(imageSize,numClasses,'EncoderDepth',5);

%% Data Augmentation

augmenter = imageDataAugmenter('RandXReflection',true,'RandYReflection',true);

pximds = pixelLabelImageDatastore(imds,pxds,'DataAugmentation', augmenter);

%% Training

options = trainingOptions('sgdm', ...

'InitialLearnRate',0.0001, ...

'Momentum',0.99, ...

'MiniBatchSize',1, ...

'MaxEpochs',300, ...

'Plots','training-progress', ...

'CheckpointPath','E:\My Project');

training = trainNetwork(pximds,lgraph(net),options);

Answer 1

[Yomna Genina]

There is no need to create a new layer graph as you already saved the last checkpoint network in the net variable which could be used directly to resume training.

Instead of the last line of code, you could do the following:

training = trainNetwork(pximds,layerGraph(net),options); % convert DAGNetwork to layer graph and resume training

This example on using a checkpoint network might be useful: https://www.mathworks.com/help/deeplearning/ug/resume-training-from-a-checkpoint-network.html