emptying each row of matrix of a in a loop then uses respective matrices produced from it to get a certain value

I have a matrix, a

a = [1 2;
    1 3;
    1 5; 
    1 7;
    1 8;];

and this matrix a, is emptied in each row per loop until the last one using this code from Matt J

a0=a;

for i=1:size(a,1)
    a=a0;
    a(i,:)=[],
end

which result in:

a = [1 3;
    1 5; 
    1 7;
    1 8;];

a = [1 2;
    1 5; 
    1 7;
    1 8;];

a = [1 2;
    1 3;
    1 7;
    1 8;];

a = [1 2;
    1 3;
    1 5; 
    1 8;];

a = [1 2;
    1 3;
    1 5; 
    1 7;];

can I create another loop to calculate a certain value, w, from the results from each loop beginning with the orginal until the last one. After each loop answer value, w, is tabulated in matrix b

b = [w
    w
    w
    w
    w
    w]

there 6 values of w since we consider the orginal a

[Ted Shultz]

Why in a seperate loop, and not at the end of the loop you have already made?

for i=1:size(a,1)
    a=a0;
    a(i,:)=[],
    % work with matrix a here
end

[JL]

Hi Ted, should i just include your code earlier here?

[JL]

for i=1:size(a,1)
    a=a0;
    a(i,:)=[],
    % work with matrix a here
end

This code actually works but it doesnt save the values from this loop into another matrix

[David Hill]

How about,

preallowcating array b = zeros(size(a,1)-1,2,size(a,1));

and having the following in the loop

b(:,:,i)=a;

Answer 1

[Matt J]

Why not as follows,

b=nan(size(a,1),1); %pre-allocate

for i=1:size(a,1)
    
    tmp=a;
    tmp(i,:)=[],
    
    b(i)=max(tmp(:))-min(tmp(:)); %example derived quantity
    
end

[JL]

Not working. Actually, so how the code works is that when it is looping. For example, the first loop

a = a = [1 2;
    1 3;
    1 5; 
    1 7;
    1 8;];

value of w is computed, let say w = 1 +1 = 2;

then 2nd loop

a = [1 3;
    1 5; 
    1 7;
    1 8;];

another w is computed, let say w=1+2=3;

then 3rd loop

a = [1 2;
    1 5; 
    1 7;
    1 8;];

value of w computed, let say w=1+3=4; then the 4th loop, then 5th loop. All the values of w after 5th loop are compiled in b

b=[ w; % from first loop
    w; % from second loop
    w; % from third loop
    w; % from fourth loop
    w; % from fifth loop
    ];

[Matt J]

Not working

Works fine for me. Here is the output from the example I posted,

b =

     7
     7
     7
     7
     6

[JL]

Hi Matt, yup it is not working for me. in fact, my matlab is going crazy.

for i=1:size(a,1)
    a=a0;
    a(i,:)=[],
    % I PLACE CODE HERE TO CALCULATE Ws
end

This code above actually produces all the calculated values of w for each loop. But I need a code to put the values of w derived from each loop into a matrix, b.

b = [250; %from first loop
    175;  %from second loop
    145;  %from third loop
    230;  %from fourth loop
    250;  % from fifth loop
    ];

[David Hill]

best to pre-allowcate as Matt discribed. you could b=[]; outside loop and b=[b,w];inside loop. Matt's solution works best.

[JL]

Thank you!