How to access a element of a dynamically created array

Hi all, I have created a set of arrays of dimension 1*3 using the following code :

BS = 3; area = 300;

X1 = area * rand(1,BS) -area/2 ;

Y1 = area * rand(1,BS) -area/2 ;

for i = 1:BS

eval(['BS' num2str(i) '= [X1(i) Y1(i) 1] '])

end

and i would like to dynamically access the third element of BS"i". Let's say that BS1(3) = 100, and BS2(3) = 150 and BS3(3) = -200. How I would realize that dynamically by using a for loop ?

[DGM]

You know what's better than solving an unnecessary problem?

Not creating the problem in the first place.

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Side note: There's not much point accessing BSx(3). You explicitly set them all to 1.

Answer 1

[DGM]

Just use an array

BS = 3; 
area = 300;

BSx = [area*(rand(BS,2) - 0.5) ones(BS,1)]

BSx = 3×3

49.0217 81.9383 1.0000 -61.5512 72.0274 1.0000 -98.1272 -102.9906 1.0000

[Akram RAYRI]

thank you for your replay, but i wanted to have each line of the created array BSx in a separated variable, because i will use each one of them later. Anyways I found a solution in order to access a specific element with the created variables using for loop that i mentioned earilier, and the solution is in fact :

eval(['BS' num2str(i) '(3) '])

with this line of code I'm accessing the third element of the each BS"i", for instance : BS1(3) = 1 and BS2(3) = 1 and BS3(3) = 1

[DGM]

I never said it couldn't be done; I said it was unnecessary. You're defeating the most basic functionality of the language by embedding indexing information into the variable name.

Accessing the row vectors within a matrix is easier, faster (by about three orders of magnitude), and more flexible than doing the same with a bunch of dynamically accessed named vectors.

BS = 3; 
area = 300;
BSx = [area*(rand(BS,2) - 0.5) ones(BS,1)]

BSx = 3×3

58.9408 15.3944 1.0000 -64.1582 65.8407 1.0000 -81.9446 -23.0681 1.0000

You want the first element of the second vector?

BSx(2,1)

ans = -64.1582

Want the third vector in whole?

BSx(3,:)

ans = 1×3

-81.9446 -23.0681 1.0000

Want all x values?

BSx(:,1)

ans = 3×1

58.9408 -64.1582 -81.9446

It's your choice.

[Akram RAYRI]

Yes I saw what you meant. Thank you so much for your reply anyways ;)