Why i didn't get the complete decision tree(I mean all attributes)? - matlab

Question

I used decision tree classifier in MATLAB. I used 7 attributes.But when i draw the decision tree it doesn't includes all attributes,it only includes 2 or 1 attributes.What is the problem of my code?
vars = {'Asymmetry' 'Border irregularity' 'colors' 'contrast' 'Co-relation'
'Homogeneity' 'Energy'};
x = [0.148 0.298 3 0.027 0.959 0.992 0.692
0.248 0.462 3 0.015 0.997 0.996 0.837
0.683 0.827 3 0.030 0.974 0.989 0.634
0.170 0.509 3 0.065 0.964 0.977 0.399
0.663 0.764 3 0.061 0.945 0.983 0.645
0.641 0.671 3 0.050 0.953 0.987 0.703
0.653 0.796 2 0.062 0.961 0.981 0.528
0.458 0.704 2 0.019 0.934 0.993 0.852
0.555 0.729 2 0.087 0.976 0.980 0.380
0.454 0.657 2 0.059 0.953 0.982 0.467
0.379 0.497 2 0.058 0.976 0.979 0.445
0.443 0.486 2 0.034 0.896 0.998 0.810
0.194 0.342 2 0.012 0.956 0.997 0.895
0.248 0.462 3 0.015 0.977 0.996 0.837
0.155 0.340 2 0.010 0.930 0.966 0.911
0.458 0.704 2 0.019 0.934 0.993 0.852];
y = {'Cancer';'Cancer';'Cancer';'Cancer';'Cancer';'Cancer';'Cancer';'Cancer';'Cancer';'Cancer';'Cancer';'Cancer';'non-Cancer';'non-Cancer';'non-Cancer';'non-Cancer'};
t = fitctree(x,y,'PredictorNames',vars, ...
'CategoricalPredictors',{},'Prune','off');
view(t);
X1=[0.148 0.186 2 0.139 0.984 0.992 0.558]
label = predict(t,X1);
view(t,'mode','graph');
The output image of the code:

Answer 1

There's nothing wrong with your code - the decision tree is not designed to use all of your variables, it's just designed to use the variables that give the best fit based on the given decision criteria. Using all of the variables would result in overfitting, especially considering that some of your variables are correlated with each other.