Matrix basic operation error

I have following code A =

     1     1     1
     2     2     2
     3     3     3
m =

     2     4     6

and I am calculating A + m

And I am getting error

Error using + Matrix dimensions must agree

similar to h ttps://www.mathworks.com/help/matlab/ref/plus.html#bu90zu2

What is wrong in my code.

[Torsten]

What result do you expect from your "a+b" operation ?

Best wishes

Torsten.

[Maryada Maryada]

I want to add m to each row of A result should be

3 5 7
4 6 8
5 7 9

[Torsten]

m must be a column vector:

m = [2;4;6]

Best wishes

Torsten.

[Steven Lord]

This behavior is known as implicit expansion and was added to the arithmetic operators like + in release R2016b.

Answer 1

[KL]

For the "edited" question,

A =[1     1     1
    2     2     2
    3     3     3]
m =[2     4     6]
c = bsxfun(@plus,A,repmat(m,3,1))

[Maryada Maryada]

Thanks a lot

[Jan]

@KL: If you use bsxfun, you can omit the repmat.

[KL]

oh yes, that's right, thanks Jan!

Answer 2

[Jan]

In modern (>= 2016b) Matlab versions use:

A = [1     1     1; ...
     2     2     2; ...
     3     3     3];
m = [2     4     6];

A + m

For older Matlab versions:

bsxfun(@plus, A, m)

[Maryada Maryada]

Thanks

Answer 3

[KL]

If you enter your code on your command window,

    >>  a = [1 2 3 4]
    b = [5; 6; 7]

you would see

a =

       1     2     3     4

b =

       5
       6
       7

which mean 'a' has 1 row and 4 columns and 'b' has 1 column and 3 rows. Basically if you want to add two matrices, they should be of same size so you can add the corresponding elements to produce a resultant matrix of the same dimension. For example,

a = [1 2 3]
b = [5 6 7]

here, this gives you

a =

       1     2     3

b =

       5     6     7

both 'a' and 'b' have 1 row and 3 columns. If you add them like you did in your question

>> c = a+b

then you will get

c =

       6     8    10

each value of 'c' is simply the sum of corresponding elements in 'a' and 'b'. If you want to do matrix multiplication, it's a little more complicated so I'd suggest you ask another question or simply have a read here .

[Maryada Maryada]

I want to add m to each row of A result should be

3 5 7
4 6 8
5 7 9