MATLAB: What’s the difference using .* and *, or ./ and /

MATLABmatrixquestion

Hi when do I know to use the . in dividing or multiplying? Originally, I had thought to use .* or ./ if we are doing element-by-element product/division of two matrices, and use * for matrix multiplication/division. If it's related to the array/vector/matrix stuff, I'm a bit fuzzy on that too, so any explanations would be great!!

Thanks!!

Best Answer

Element-by-element operations. These are obtained using .* , .^, ./, or .\. See the Arithmetic Operators page. See

Related Solutions

MATLAB: What are ./ and .* are used for

./ and .* are element-by-element division and multiplication, respectively.

[1 2 3] ./ [4 5 6]

means

[1/4 2/5 3/6]

and

[1 2 3] .* [4 5 6]

means

[1*4 2*5 3*6]

The operations that do not have the dots in them, / and * are instead matrix algebra division and matrix algebra multiplication

MATLAB: Can’t I multiply two arrays using the ‘*’ operator

Because the dot operator does element-wise multiplication (and division and exponentiation). These are termed array operations in MATLAB.

If you do not use the dot operator, you are using standard linear algebra matrix operations, and those require that you follow the rules for array operations from linear algebra.

array1 = [1,2,3];
array2 = [4,5,6];
Result1 = array1' * array2;         % 3x3 Matrix (Matrix Multiplication)
Result2 = array1 * array2';         % Scalar (Dot Product)
Result3 = array1 .* array2;         % 1x3 (Element-Wise Multiplication)

See the documentation on Array vs. Matrix Operations (link) for details.

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Related Solutions

MATLAB: What are ./ and .* are used for

MATLAB: Can’t I multiply two arrays using the ‘*’ operator

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