How do count the number under multiple conditions?

I have four numbers (A, B, C, D) that may be different. I would like to count the number such as A=B=C=D, A~=B~=C~=D, or A=B, C=D, but A~=C, etc. My codes are as follows, but the answers are wrong. Please check why?

Thank you very much.

A=3; B=3; C=3; D=3; %% Case-1 The answer should be Q1=1 and Q2=...Q16=0

Q1=sum(A==B==C==D)

Q2=sum(A~=B~=C~=D)

Q3=sum(A==B & C==D & A~=C)

Q4=sum(A==C & B==D & A~=B)

Q5=sum(A==D & B==C & A~=B)

Q6=sum(A==B==C & C~=D)

Q7=sum(A==B==D & C~=D)

Q8=sum(A==C==D & A~=B)

Q9=sum(B==C==D & A~=D)

Q10=sum(A==B==D & A~=C)

Q11=sum(A==B & C~=D & A~=C)

Q12=sum(A==C & B~=D & A~=B)

Q13=sum(A==D & B~=C & A~=B)

Q14=sum(B==C & A~=D & B~=A)

Q15=sum(B==D & A~=C & B~=A)

Q16=sum(C==D & A~=B & C~=A)

A=3; B=3; C=3; D=5; %% Case-2 The answer should be Q6=1 and others=0

Answer 1

[Image Analyst]

Use && instead of &.

And you can only compare pairs, so you can't do

Q1=sum(A==B==C==D)

but you can do

Q1=sum(A==B && A==C && A==D && B==C && B==D && C==D)

Of course it's best if you just use histogram() and look at the counts in each bin.