change 'classWeights' in unetLayers

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Marco Festugato
Marco Festugato 2019-9-16
评论： Timothy Lee 2020-6-8
Hello,
im using Unet to perform semantic segmentation (I want to segment liver metastasis). I want to weight 'more' the pixels of the metastasis respect to the background but I can't manage to do it...
Code for creating unet architecture:
lgraph = unetLayers(imageSize, numClasses, 'EncoderDepth', 4);
How can I change the 'classWeights' in lgraph.Layers(end).pixelClassificationLayer in order to do this??
If, for example, I do this:
lgraph.Layers(end).pixelClassificationLayer.classWeights = [2, 0.5];
I receive an error telling me that i have first to put the 'labels' to the 'classes' options in lgraph.Layers(end), but if i do this:
lgraph.Layers(end) = {'metastasis', 'background'};
I receive an error telling that that layer is in 'read only' mode....
Please im getting crazy...
Thanks in advance for any help!

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采纳的回答

Raunak Gupta
Raunak Gupta 2019-9-19
Hi,
The unetLayers object in MATLAB is in read only mode and we cannot change the properties of layers as such. You may remove the last layer which is the Segmentation-Layer and can add a new Segmentation-Layer with the properties that are mentioned. Following Code will help.
% Last Layer Name is 'Segmentation-Layer'
% for checking layer name use :- lgraph.Layers
lgraph = removeLayers(lgraph,'Segmentation-Layer');
layerlast = pixelClassificationLayer('Classes',{'metastatis','background'},'ClassWeights',[2,0.5],'Name','New_segmentation_Layer');
layer_to_add = [layerlast];
lgraph = addLayers(lgraph,layer_to_add);
Reference to the functions that are used removeLayers, pixelClassificationLayer, addLayers.
  2 个评论
Timothy Lee
Timothy Lee 2020-6-8
By using pixelClassificationLayer with class weights, is this the same as implementing a custom weighted classification layer, as shown in this example:
https://de.mathworks.com/help/deeplearning/ug/create-custom-weighted-cross-entropy-classification-layer.html

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