Given a Matrix A, create a row vector of 1s that has same number of elements as A has rows

Question

Gaurav Srivastava 2019-6-4

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows

评论： Voss 2024-2-2

Given a Matrix A, Create a row vector of 1's that has same number of elements as A has rows. Create a column vector of 1's that has the same number of elements as A has columns. Using matrix multiplication, assign the product of the row vector, the matrix A, and the column vector (in this order) to the variable result. A = [1:5; 6:10; 11:15; 16:20];

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Alex Mcaulley 2019-6-4

See this:

Matlab tutorials

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Manali Gupta 2021-5-20

9
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows#answer_377756

编辑：MathWorks Support Team 2021-5-20

R_vector = ones(1,size(A,1)); C_vector=ones(size(A,2),1); result = R_vector*A*C_vector;

4 个评论
显示 2更早的评论隐藏 2更早的评论

Aadesh Navade 2020-5-29

can you explain the syntax row and column

Mariam Aldeepa 2021-1-2

Why when you calculate the result multiplied the matrix "A" with another two matrices ?

请先登录，再进行评论。

Answer 2

Alex Mcaulley 2019-6-4

7
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows#answer_377771

I think the goal of this forum is not to do anyone's homework, but to solve generic questions about Matlab that can help more users. This exercise is very simple, anyone who has ever used Matlab could do it, so, I think the best thing we can do is help @Gaurav to know how to learn the basics of Matlab.

2 个评论
显示无隐藏无

Carlo Romagnolo 2021-4-19

在 MATLAB Online 中打开

Hi! I know this might be a long a shot, as this thread has been inactive for quite some time, but I was wondering if you could help me with a general question on this.

Here is my code to solve this problem:

A = [1:5; 6:10; 11:15; 16:20];
format compact
row = [1,1,1,1]
column = [1;1;1;1;1]
result = row * A * column

I was wondering if there is a better/more elegant way to answer the question which does not involve hardcoding the row and column vectors but instead uses functions.

Walter Roberson 2021-4-19

ones(1,size(A, 1))

请先登录，再进行评论。

Answer 3

Khom Raj Thapa Magar 2020-8-28

7
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows#answer_486311

编辑：DGM 2023-2-21

在 MATLAB Online 中打开

% Given 
A = [1:5; 6:10; 11:15; 16:20];
row_vec = ones(1,size(A,1))
row_vec = 1×4
     1     1     1     1
column_vec = ones(length(A),1)
column_vec = 5×1
     1
     1
     1
     1
     1
result = row_vec * A * column_vec
result = 210

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

DGM 2023-2-21

The length() function does not return the number of columns in an array. It returns the size of the longest dimension. If A has more rows than columns, this code will fail. Use size() to get the size of a specific dimension.

请先登录，再进行评论。

Answer 4

Sudhanshu Rasal 2020-5-5

4
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows#answer_430426

编辑：DGM 2023-2-21

在 MATLAB Online 中打开

Simple way to do this question is

X=[1 1 1 1]
Y=[1;1;1;1;1]
result=X*A*Y

????????

3 个评论
显示 1更早的评论隐藏 1更早的评论

el mehdi latrach 2020-6-14

no, it does not work ,

it shows error

DGM 2023-2-21

编辑：DGM 2023-2-21

在 MATLAB Online 中打开

The point of writing a program is to have the computer do the work. Literally writing out the vectors manually makes as much sense as calculating the inner product on paper and writing

result = 210; % this is my entire program

Both examples will fail for obvious reasons if the size of A changes.

请先登录，再进行评论。

Answer 5

Tushar Parmar 2020-5-11

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows#answer_431802

在 MATLAB Online 中打开

A = [1:5; 6:10; 11:15; 16:20]
B(1:4)=1;
f=B*A
C(1:5)=1;
C=C'
result=f*C

6 个评论
显示 4更早的评论隐藏 4更早的评论

Tharindu Priyankara 2020-8-29

THANKS

DGM 2023-2-21

The point of writing a program is to have the computer do the work. Use size() to find the size of A; use ones() to generate the vectors programmatically.

请先登录，再进行评论。

Answer 6

Arakala Gautham 2020-4-4

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows#answer_423904

在 MATLAB Online 中打开

R_vector = ones(1,size(A,1));
C_vector=ones(size(A,2),1);
result = R_vector*A*C_vector;

5 个评论
显示 3更早的评论隐藏 3更早的评论

DGM 2023-2-21

Note that the accepted answer was copy-pasted verbatim from this answer.

Abhishek 2023-7-2

在 MATLAB Online 中打开

A = [1:5; 6:10; 11:15; 16:20];
R = (A(:,1))';
R(:)=1;
C = (A(1,:))';
C(:)=1;
result = R*A*C
%@DGM bro is this code ookay?

请先登录，再进行评论。

Answer 7

Rishabh Nirala 2020-5-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows#answer_434603

编辑：DGM 2023-2-21

在 MATLAB Online 中打开

A = [1:5; 6:10; 11:15; 16:20];
C = [1;1;1;1;1]
R = [1 1 1 1 ]
P = R * A
result = P*C

ANSWER = 210

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

DGM 2023-2-21

Again, the point of writing a program is to have the computer do the work. Use size() to find the size of A; use ones() to generate the vectors programmatically.

请先登录，再进行评论。

Answer 8

Sneham Shrikant Vaidya 2020-5-27

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows#answer_440539

编辑：DGM 2023-2-21

在 MATLAB Online 中打开

A = [1:5; 6:10; 11:15; 16:20];
A
x = [1 1 1 1 ]
y = [1;1;1;1;1]
z = A*y
result =x*z

you can also perform this way as we know z =(lxm)*(mxn) so we first multiply A*y as their inner dimension ara same

then we obtain result matrix z that has inner dimension equal to x so now we can multiply x*z to get final ans

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

DGM 2023-2-21

Use size() to find the size of A; use ones() to generate the vectors programmatically. Otherwise, this fails if the size of A changes.

Adding explanations to your answers is good though.

请先登录，再进行评论。

Answer 9

VISHWA D 2020-6-22

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows#answer_455455

在 MATLAB Online 中打开

A = [1:5; 6:10; 11:15; 16:20];
row_vector=[1 1 1 1 1]
col_vector=[1; 1; 1; 1]
result=(row_vector*(A'))*(col_vector)

2 个评论
显示无隐藏无

lijuan wang 2020-8-27

I thought the assignment has a wrong requirement, right?

we should create a vector which has the some rows as A. So it should be row_vector=[1 1 1 1]'?

DGM 2023-2-21

编辑：DGM 2023-2-21

@lijuan wang is correct. This answer creates the vectors incorrectly. Not only are they created manually in a way that would break if the size of A changes, they do not correspond to the specified dimensions of A. The result is correct, but the vectors are wrong, and the method is poor practice.

请先登录，再进行评论。

Answer 10

Chintan 2023-2-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows#answer_1175970

在 MATLAB Online 中打开

row_vector=ones(size(A(:,1)))'
coloumn_vector=ones(size(A(1,:)))'
result=row_vector*A*coloumn_vector

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

DGM 2023-2-21

I suppose that's one way, but size() supports dimension specification, which would avoid the need to address vectors of A or to transpose anything.

Also note that the ctranspose, ' operator is the complex conjugate transpose. If you just want to reorient a vector or matrix, use transpose, .' instead.

请先登录，再进行评论。

Answer 11

Waseem Zafar 2023-9-17

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465444-given-a-matrix-a-create-a-row-vector-of-1s-that-has-same-number-of-elements-as-a-has-rows#answer_1312022

编辑：Waseem Zafar 2023-9-17

A = [1:5; 6:10, 11:15; 16:20]

R = [1 1 1 1]

C = [1;1;1;1;1]

Z = A*C

result = R*Z

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

DGM 2023-9-17

在 MATLAB Online 中打开

This example is identical to at least two other bad examples in this thread, differing only in the variable names.

You are told to use the size of A to construct two vectors. This example, and at least four others define the vectors literally instead of programmatically creating them as told. Let me be clear. You literally wrote two of the intermediate results into the script instead of making your script calculate them. If I were grading this, I would accept it no more than if you had just written

result = 210;

... because it neglects the entire point of the exercise to presuppose the input and bake the results into the script as literals.

An answer can earn its place if it demonstrates something either good or bad, but there is no value in duplicate, unformatted, unexplained answers with obvious, openly-discussed flaws. It doesn't add anything to the discussion and only serves to confuse readers who are looking for help.

Is there always room left in a thread for another answer that's not a near-duplicate? No. Sometimes it's not. Is this question completely exhausted? Not sure, but with extremely simple direct questions, it doesn't take long. If you want to answer questions, pick a thread where there is still room for a new answer.

请先登录，再进行评论。