I don't understand why the matrix dimensions are exceeded

A= zeros(3,10);
A(1,:)=[1:10];
B=.5+rand(1,10)*.4;
A(2,:,:)=B;
C=round(1+rand(1,10)*7);
A(3,:,:)= C;
A

team_A= zeros(3,5);
team_B= zeros(3,5);
for d=[1:1:10]
    if rem(d,2)==1;
    for e=[1:1:10]
    if A(2,e)== max(B)
        p=e;
        team_A(:,2,:)=A(:,p,:);
        A(:,p)=[];
    end
    end
    elseif rem(d,2)==0
        for f=[1:1:10]
            if A(2,f)== max(C);
            i=f;
            team_B(:,2,:)=A(:,i,:);
            A(:,i)=[];
            end
        end
    end
end 

Index exceeds matrix dimensions.

Error in JAS_HW4 (line 14)
    if A(2,e)== max(B)

[Jacob Savona]

A= zeros(3,10); A(1,:)=[1:10]; B=.5+rand(1,10)*.4; A(2,:,:)=B; C=round(1+rand(1,10)*7); A(3,:,:)= C; A

team_A= zeros(3,5); team_B= zeros(3,5); for d=[1:1:10] if rem(d,2)==1; for e=[1:1:10] if A(2,e)== max(B) p=e; team_A(:,2,:)=A(:,p,:); A(:,p)=[]; end end elseif rem(d,2)==0 for f=[1:1:10] if A(2,f)== max(C); i=f; team_B(:,2,:)=A(:,i,:); A(:,i)=[]; end end end end

Answer 1

[Star Strider]

I believe I see the problem.

In these lines:

A(:,p)=[];

and

A(:,i)=[];

you’re shortening ‘A’ by one column. If you want empty values in your array, you either have to set them equal to NaN (in a numeric array), or if you decide to use a cell array, it will tolerate empty entries.

I would change them both to:

A(:,p)=NaN;

and

A(:,i)=NaN;

respectively. Your code will run with that change without throwing the error, but you may have more work to do to make it give you the results you want.

[Jacob Savona]

That worked! Now it won't go to the elseif statement when rem(d,2)==0... Here's my code now:(I changed it so that it will select from a new matrix minus the one i deleted) A= zeros(3,10); A(1,:,:)=[1:10]; B=.5+rand(1,10)*.4; A(2,:,:)=B; C=round(1+rand(1,10)*7); A(3,:,:)= C; A

team_A= zeros(3,5); team_B= zeros(3,5); for d=[1:1:10] j=10; k=9; if rem(d,2)==1; for e=[1:1:j] if A(2,e,:)== max(B) p=e; team_A(:,2,:)=A(:,p,:); A(:,p)=NaN; end end elseif rem(d,2)==0 for f=[1:1:k] if A(2,f,:)== max(C) i=f; team_B(:,2,:)=A(:,i,:); A(:,i)=NaN; end end end j=j-2; k=k-2; end

[Star Strider]

I’m glad it worked!

I would appreciate it if you would Accept my Answer if it solved your problem.

[Star Strider]

Jacob Savona’s ‘Answer’ moved here...

Here is my new code: It doesn't go to the ifelse statement when the condition of the if statement isn't met...should be just else?

A= zeros(3,10);
A(1,:,:)=[1:10];
B=.5+rand(1,10)*.4;
A(2,:,:)=B;
C=round(1+rand(1,10)*7);
A(3,:,:)= C;
A

team_A= zeros(3,5);
team_B= zeros(3,5);
for d=[1:1:10]
    j=10;
    k=9;
    if rem(d,2)==1;
    for e=[1:1:j]
    if A(2,e,:)== max(B)
        p=e;
        team_A(:,2,:)=A(:,p,:);
        A(:,p)=NaN;
    end
    end
    elseif rem(d,2)==0
        for f=[1:1:k]
            if A(2,f,:)== max(C)
            i=f;
            team_B(:,2,:)=A(:,i,:);
            A(:,i)=NaN;
            end
        end
    end
    j=j-2;
    k=k-2;
end

[Star Strider]

Whether you use ‘elseif’ or ‘else’ there shouldn’t matter. I don’t follow what you’re doing, so I can’t comment on the logic in your code.

The problem is that you closed the first ‘if’ statement with an ‘end’, so it will never enter the ‘elseif’ structure. Eliminate the second ‘end’ and it should work.

Illustrating:

    for e=[1:1:j]
    if A(2,e,:)== max(B)
        p=e;
        team_A(:,2,:)=A(:,p,:);
        A(:,p)=NaN;
    end
    end     <— ELIMINATE THE SECOND ‘end’ HERE

Answer 2

[Image Analyst]

Do you remember when you did this:

A(3,:,:)= C;

and made A into a 3D matrix? Well, what are you doing when you do this:

if A(2,e)== max(B)

Why did you not pass in three indexes for the 3D matrix A??? You passed in only 2 instead of 3. Fix that.

Also, don't compare floating point values like that. Why not? See the FAQ: http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

[Jacob Savona]

I switched A(2,e)==max(B) to A(2,e,:)==max(B). That did not work. I'm trying to select a certain column of the second row for matrix A, then put those values into team_A. Then delete those selected values from matrix A.

[Image Analyst]

Change the first part of your code to this:

A = zeros(3,10);
A(1,:) = [1:10];
B = 0.5 + rand(1,10) * 0.4;
A(2,:) = B;
C = round(1+rand(1,10)*7);
A(3,:) = C;
A
max(B)
max(C)

Then, you're setting a row of A equal to [], which shortens it by a column, so you can't go up to column 10 like you originally planned - there aren't that many columns anymore because you deleted one!