How to avoid adding same elements

Hello,

I have one question.

I need to sum elements of an matrix 1x7, but I need to exclude same elements.

For example

a=[5 4 3 2 1 1 6]

I would like to get b=5+4+3+2+1+6, not 5+4+3+2+1+1+6.

Answer 1

[Dyuman Joshi]

You can use unique to get the elements without repetition (subject to sum being less than 9007199254740992, as mentioned below)

%random data
a=[5 4 5 3 2 6 1 6 1 6];
b=unique(a,'stable') 

b = 1×6

5 4 3 2 6 1

%using 'stable' to give an idea about the order
%you can use unique without 'stable' option as well
s=sum(b)

s = 21

Edit - In case you are dealing with fractional number, as @Walter Roberson commented,

sum(unique(a)) and sum(unique(a,'stable')) won't give the same answer.

Read - Why 0.3-0.2-0.1 not equal to 0

[Walter Roberson]

If you turn out to be working only with integers, and your sum will not exceed 9007199254740992 then you can use

sum(unique(a))

without the 'stable' option.

However if you have fractions such as [.1 .2 .3] then the order of summation can make a difference to the last few bits of the final result.

[Dyuman Joshi]

I am aware that one can use unique() without the 'stable' option, I just used stable option to give a hint.

Though you are right about fractions, I will edit my statement in my answer accordingly.

format long e
flintmax

ans = 
     9.007199254740992e+15

[MIch]

Thank you very much for your help.