how to average column 3 when column 1 and column 2 satisfies some condition in matrix

i have a n*3 matrix as shown below

A    B    C
1    1    2
1    2    22
1    2    12
1    3     0
1    3     4
2    2     6
2    2     0
2    3     2
2    3     2

I need the result as

A     B     C
1     1     2
1     2     17   # average  
1     3     4    #no need to average if value =0
2     2     6
2     3     2

[Luna]

What is the rule of the condition could you please explain?

And how it relates with the A and B columns?

Answer 1

[Andrei Bobrov]

T = readtable('file1.txt');

or

M = [1    2    22
1    2    12
1    3     0
1    3     4
2    2     6
2    2     0
2    3     2
2    3     2];

T = array2table(M,'v',{'A','B','C'});

solution:

out = varfun(@(x)sum(x)/nnz(x),T,'GroupingVariables',{'A','B'});

[anas ibnu]

thank you . it works

would you please explain the logic in the function

@(x)sum(x)/nnz(x)

[Andrei Bobrov]

@anas: please read about function nnz.

Answer 2

[KSSV]

A = [1    2    22
1    2    12
1    3     0
1    3     4
2    2     6
2    2    0
2    3     2
2    3     2];

[c,ia,ib] = unique(A(:,1:2),'rows') ;
iwant = c ;
m = zeros(length(c),1) ;
for i = 1:size(c,1)
    T = A(ib==i,3) ;
    if abs(min(T))>0
        m(i) = mean(T) ;
    end
end
iwant = [ iwant m] ;

[anas ibnu]

i hope this will work on proper altration

now theproblem is, its not geting the required matrix of format n/2 *3

Answer 3

[madhan ravi]

Note: Problem is unclear still. Are you sure about your desired result ? What's the condition ? How did you get 2 2 2 at the end ?

A=a(1:2:end,:);
B=a(2:2:end,:);
for i = 1:size(A,1)
    if A(i,end) || B(i,end) ~= 0 
    B(i,end)=(A(i,end)+B(i,end))/2;
    end
end
Result = B

Gives:

Result =
     1     2    17
     1     3     2  % (2+2)/2 = > 2 How did you get 4 , if you say average?? 
     2     2     3
     2     3     2

[anas ibnu]

it is just sum only

i need the average

[anas ibnu]

if either the values = 0 no need to average

[anas ibnu]

i am sorry the last line was wrong

this is my n*3 matrix

A B C

1 1 4

1 2 22

1 2 12

1 3 0

1 3 4

2 2 6

2 2 0

2 3 2

2 3 2

and i need answer as (n/2)*3 matrix1

A B C

1 1 4

1 2 (22+12)/2 # average

1 3 4 #no need to average if value =0

2 2 6

2 3 2