The number of left parenthesis is not equal to the number of right parenthesis in your
nneval.m Line: 18.. You may look into the code by clicking this error message, and count the number of left parentheses and right parentheses on the line of code.
I checked out the
nneval.m file from github. What's your Matlab version? Try to change line 18 to :
[er_train, tmp] = nntest(nn, train_x, train_y);
If your input has 6 argument, change line 22 as well:
[er_val, tmp2] = nntest(nn, val_x, val_y);
The error message should be eliminated.