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

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];

[Alex Mcaulley]

See this:

Matlab tutorials

Answer 1

[Manali Gupta]

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

[Ayush Khandelwal]

Result show error

[kesava rao]

row=ones(1,size(A,1))
column=ones(length(A),1)
result=row*A*column

[Aadesh Navade]

can you explain the syntax row and column

[Mariam Aldeepa]

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

Answer 2

[Alex Mcaulley]

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.

[Carlo Romagnolo]

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]

ones(1,size(A, 1))

Answer 3

[Khom Raj Thapa Magar]

% 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

[DGM]

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.

Answer 4

[Sudhanshu Rasal]

Simple way to do this question is

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

????????

[Aadesh Navade]

yeah i got the same result for this too

[el mehdi latrach]

no, it does not work ,

it shows error

[DGM]

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.

Answer 5

[Tushar Parmar]

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

[Ayush Khandelwal]

Thanks bhai

[Ayush Khandelwal]

Give me the answer of this question as systematic way

[ASWATHI V]

THANK YOU

[Jeeva G]

Thank you!!!!

[Tharindu Priyankara]

THANKS

[DGM]

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.

Answer 6

[Arakala Gautham]

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

[Sudhanshu Rasal]

It will not show the result in command window??? You used colon at the end of result?

[Ayush Khandelwal]

Kya Kare error aa raha hai

[Aadesh Navade]

remove that colon(;) from the last line

[DGM]

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

Answer 7

[Rishabh Nirala]

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

[DGM]

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.

Answer 8

[Sneham Shrikant Vaidya]

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

[DGM]

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.

Answer 9

[VISHWA D]

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)

[lijuan wang]

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]

@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.

Answer 10

[Chintan]

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

[DGM]

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.