matrix dimension must agree

Hi,

I am trying to do CKNN. The script runs smoothly at first. But when I try to see confusion matrix, Iget error saying Matrix dimension must agree.

Why is this happenning?

load('Assignment 2\ENN543_Assignment2_Data\Q3\mnist_train.mat')

mnist_images_train = reshape(imgs,1024,50000);
mnist_train_y = labels;
load('Assignment 2\ENN543_Assignment2_Data\Q3\mnist_test.mat')
mnist_images_test = reshape(imgs,1024,10000);


mnist_test_y=labels;
load("Assignment 2\ENN543_Assignment2_Data\Q3\svhn_test.mat")
svnh_images_test=reshape(imgs,1024,26032);
svnh_test = labels;
%%-CKNN
% cknn = fitcknn(mnist_images_train',categorical(mnist_train_y), 'Distance', 'cityblock');
cknn = fitcknn(mnist_images_train',mnist_train_y,'NumNeighbors',5);
pred = cknn.predict(mnist_images_test')
disp(sum(pred == mnist_test_y)/length(mnist_test_y))
%%Matrix dimension must agree
confusionchart(mnist_test_y, pred)

[Ajay Pattassery]

can you post the output of size(mnist_test_y) and size(pred)