An interactive introduction to MATLAB

10 basic concepts

12 35 32

13 29 41

14 >> a.*b

15 ans =

16 8 21

17 45 6

18 >> c = [1 2 3 4]

19 c =

20 1 2 3 4

21 >> a*c

22 ??? Error using ==> mtimes

23 Inner matrix dimensions must agree.

24 >> a.*c

25 ??? Error using ==> mtimes

26 Matrix dimensions must agree.

Comments:

• The dot operator signifies an element-by-element operation. The dot
  can be used for multiplication.*, division./, or exponentiation.^of
  elements of vectors that are the same size. Omitting the dot before an
  arithmetic operator meansMATLABperforms the matrix version of the
  operation.


• On Line 21 we tried to perform a matrix multiplication of a 2×2 matrix
  with a 1×4 matrix. This results in an error because you can only multiply
  two matrices if the number of columns in the first equals the number of
  rows in the second.


• On Line 24 we get a similar error if we try to perform an element-by-
  element multiplication, as this does not make any sense for matrices of
  different sizes.

Table 2: Element-by-element arithmetic operations

command description

.* Element-by-element multiplication

./ Element-by-element division

.^ Element-by-element exponentiation

The dot operator

(http://www.eng.ed.ac.uk/teaching/courses/matlab/unit01/dot-

operator.shtml)