how to create a series of changes over the loop variable and can assign a value to it

how to create a series of changes over the loop variable and can assign a value to it Example

for r=1:3
  A|r| = r 
  B|r| = A|r+1| + A|r|
end
the result
A1=1
A2=2
A3=3
B1=3
B2=5
...

Answer 1

[Youssef Khmou]

try :

 n=1:30;
 A=n;
 for r=1:length(n)-1

   B(r)=A(r+1)+A(r);
 end

plot(A), hold on, plot(B)

[Pham Ngoc Thanh]

Thanks so much, but I my question can explain follows: I have a matrix [3x4]( rand(3,4), I create A0 variable and assign A0=rand(3,4). I want to create A1 = rand(3,4+1), A2=rand(3,4+2)...Ai=rand(3, 4+i).

for i=1:4
  Ai = rand(3,4+i)
end

Please help me

[Youssef Khmou]

hi, In this case, the dimension grows inside the loop so you need to use the cell :

 for i=1:4
  A{i}=rand(3,4+i);
 end

[Pham Ngoc Thanh]

Hi I have tried

for i=1:4

A{i}=rand(3,4+i);

end but have an error: "Cell contents assignment to a non-cell array object" What can I do?

Answer 2

[Image Analyst]

You don't have a good condition for when r = the last value, for example, what is A(4) when r only goes to 3. But ignoring that last element, this will work for you:

n=10
A=1:n
B = A + [A(2:end) 0]

In command window:

n =
    10
A =
     1     2     3     4     5     6     7     8     9    10
B =
     3     5     7     9    11    13    15    17    19    10

If you want to add the last element of A then turn the 0 into A(n).

Answer 3

[Image Analyst]

This works just fine (if that's what you want to do):

clc;
for i=1:4
  A{i} = rand(3,4+i)
end
whos A

A = 
    [3x5 double]
A = 
    [3x5 double]    [3x6 double]
A = 
    [3x5 double]    [3x6 double]    [3x7 double]
A = 
    [3x5 double]    [3x6 double]    [3x7 double]    [3x8 double]
  Name      Size            Bytes  Class    Attributes

    A         1x4              1072  cell

See how it grows with each iteration and the size of the last-added cell is bigger each time? Just what you wanted, right?

[Pham Ngoc Thanh]

Thanks you a lot

I really want to make the variables gradually increase after each iteration to assign to the created matrix after each iteration. then use these variables in other calculations

 example:
   A{0} = rand(3,4);
   for i=1:4
     A{i}= rand(3.4+i);
     B{i}= A{i}*A{i+1}'
   end
and the result i want:
 A1 = [3x5]
 A2 = [3x6]
 B1 is a matric A1*A2'
....

[Image Analyst]

You can't multiply a 3x5 by a 6x3 - it doesn't work. Anyway, I see you've already accepted another answer so I guess you got it solved that way.

[Pham Ngoc Thanh]

I'm sorry. B{i} = A{i}'*{A{i+1} [5x3]*[3x6}

Now i can understand some things. Thanks you a lot.