How to use Loop without For or While

Question

Ardalan Norouzi 2015-11-29

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/258093-how-to-use-loop-without-for-or-while

评论： Jan 2015-12-6

Hello everyone Consider this code:

n=10;
m=5;
A=zeros(n,m);
A(1,:)=[1];
for i=1:n-1
    A(i+1,:)=3*A(i,:)
end

answer is :

A =
             1           1           1           1           1
             3           3           3           3           3
             9           9           9           9           9
            27          27          27          27          27
            81          81          81          81          81
           243         243         243         243         243
           729         729         729         729         729
          2187        2187        2187        2187        2187
          6561        6561        6561        6561        6561
         19683       19683       19683       19683       19683

How can I calculate the A without using For (or while) , like this code:

n=10;
m=5;
A=zeros(n,m);
A(1,:)=[1];
A(2:end,:)=3*A(1:end-1,:)

unfortunately this code appears this:

A =
   1     1     1     1
   3     3     3     3
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0

Thanks every one

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James Tursa 2015-11-29

编辑：James Tursa 2015-11-29

Is this homework? What's wrong with using your loop?

Ardalan Norouzi 2015-11-29

编辑：Ardalan Norouzi 2015-11-29

yes it's question of my teacher for homework please help me

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Answer 1

Walter Roberson 2015-11-29

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/258093-how-to-use-loop-without-for-or-while#answer_201547

See bsxfun

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Jan 2015-11-29

编辑：Jan 2015-11-29

@Ardalan Norouzi: It is your homework. If the complete solution is posted in the forum, you have to cheat when you submit it. you can find the solution by your own, when you read the documentation of bsxfun.

Ardalan Norouzi 2015-11-29

编辑：Ardalan Norouzi 2015-11-29

I'm trying to write the code but I can't complete it, Please help me

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Answer 2

Jan 2015-11-29

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/258093-how-to-use-loop-without-for-or-while#answer_201562

在 MATLAB Online 中打开

2 hints:

3 .^ (0:9)
% [1, 3, 9, 27, 81, 243, 729, 2187, 6561, 19683]
[1;2;3] * [4,5,6]
% [4, 5, 6;
%  8, 10, 12;
%  12, 15, 18]

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Ardalan Norouzi 2015-11-29

编辑：Ardalan Norouzi 2015-11-29

I would like to create an array of elements which created with their last elements. for example A is an array with 1 row and 5 column , first column is 1 and second column is 3*A(first) and third column is 3*A(second) and ... The whole of this procedure without using "For" or "While"

Jan 2015-12-6

在 MATLAB Online 中打开

So what's wrong with the hints I gave?! I hesitate to post the complete solution, because otherwise you cannot submit this as a your homework without cheating. But the shown methods allow to solve the problem easily. If you do not only claim, that they do not help you but post, what you have tried and why you think, that this does not help, I had a chance to give further hints.

3 .^ (0:9).'

Now this must by multiplied by a vectors of ones to obtain the shown matrix.

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