Using MNIST in MATLAB

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Hello
I am new to OCRs and am trying to use the MNIST dataset in matlab. I found a csv version of the data set which is usable in MATLAB then stored it as a .mat file (Somehow loads faster, I'm not so sure why if you do know do tell me). I wanted to try it on the fitcknn command as such
clc, clear
close all;
load 'mnist_train.mat'
knnmodel = fitcknn(mnist_train,"Var1")
I tried the Onramp course and tried to mimic how they did it but I get these error messages. I wanted to know if I can make this work and how.
Error using classreg.learning.FullClassificationRegressionModel.prepareDataCR (line 234)
X and Y do not have the same number of observations.
Error in classreg.learning.classif.FullClassificationModel.prepareData (line 821)
classreg.learning.FullClassificationRegressionModel.prepareDataCR(...
Error in ClassificationKNN.prepareData (line 926)
prepareData@classreg.learning.classif.FullClassificationModel(X,Y,varargin{:},'OrdinalIsCategorical',true);
Error in classreg.learning.FitTemplate/fit (line 233)
this.PrepareData(X,Y,this.BaseFitObjectArgs{:});
Error in ClassificationKNN.fit (line 911)
this = fit(temp,X,Y);
Error in fitcknn (line 264)
this = ClassificationKNN.fit(X,Y,RemainingArgs{:});
Error in OCR (line 6)
knnmodel = fitcknn(mnist_train,"Var1");

Accepted Answer

larasupernovae
larasupernovae on 11 Mar 2022
So here is book, check out Chapter 6 if you are begining the MNIST in MatLab this is the best way to understand it all, hope this helps :) I also included my code from the book, a while a back when I was starting out with MNIST.
  3 Comments
Jacob Ebilane
Jacob Ebilane on 13 Mar 2022
I guess it has something to do with the algorithm I have for separating each digit. I think it has something to do with the data reaching the top of the image itself.

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