# how to create a target set for ANN classification???

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julius bamwenda on 13 Aug 2017
Commented: shivasmic on 24 Jun 2019
i am trying to create a target set for my inputs to be used in classification with ANN but i have some challenges . i have 23 classes of images of which each class contains 100 images. feature extraction was done and i got a matrix of 2300*20736. how can i create a target set for my inputs.

Baptiste Ottino on 14 Aug 2017
Your target set must have one label for each sample, so it must contains 2300 elements. Here is an easy way to build one. Start by numbering your classes from 1 to 23. Make sure that your X Array is sorted by class, meaning all the samples from the first class, then all the samples from the second class, and so on. Then:
% Classes from 1 to 23
y = 1:23;
% 100 samples per class
y = repmat(y, 100, 1);
% Reshape to obtain a vector
y = reshape(y, 1, numel(y));
At this stage, you should have a 1-by-2300 vector with numeric class labels from 1 to 23. This is what you want if you use the Statistics and Machine Learning tToolbox.
Now, I suppose you intend to use the Neural Network Toolbox. In that case the syntax is a bit different: the class labels are in a 23-by-2300 matrix, each column being a sample, with the row corresponding to the class getting value '1' and the rest '0'. To build it from the previous syntax, type:
y = full(ind2vec(y));
Good luck!

julius bamwenda on 15 Aug 2017
thanks so much. İt has really helped.
julius bamwenda on 6 Sep 2017
Hi everyone, i have applied ANN and i have successfully got good results. so now i want to apply KNN classification method on the same data. as far as KNN is concerned, i have to create a training set, sample set and lastly the group set. ie: class=knnclassify(sample,training,group). so how can i create those sets? thanks in advance
shivasmic on 24 Jun 2019
Baptiste ottino, thanx for the method, the method that you suggest for the comnstruction of target vector leads to the creation of matrix which has dimensions of 23 x 2300 but the input vector has dimension of 2300 x 20736.
Dont you think that the dimension of target vector should also be 2300 x 23.
I am asking this as I am also facing the same problem. Kindly clarify this as soon as possible!