Mathematical notation to multiply matrix elements

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Discussion Overview

The discussion revolves around the mathematical notation for multiplying elements of two matrices, specifically focusing on the componentwise multiplication of vectors. Participants explore the concept of the Hadamard product and its application in a homework context involving power calculations for a car.

Discussion Character

  • Exploratory, Homework-related, Technical explanation

Main Points Raised

  • One participant seeks clarification on the notation for multiplying matrices A and B to produce matrix C, where each element of C is the product of corresponding elements from A and B.
  • Another participant identifies this operation as componentwise multiplication of vectors.
  • A different participant suggests that the operation described resembles the dot product of two vectors, which typically results in a single scalar value.
  • A later reply clarifies that the operation is known as the Hadamard product, which produces a matrix C where each element is the product of corresponding elements from matrices A and B.
  • The original poster inquires whether this multiplication can be computed using common mathematical operators like inverse, transpose, dot product, or cross product.
  • The original poster also mentions their context of using Mathcad for a homework assignment related to calculating power requirements of a car, indicating a desire for a more efficient method than manual calculations.
  • Another participant notes that in Matlab, the notation for this type of multiplication is represented as ".*" instead of just "*".

Areas of Agreement / Disagreement

Participants express differing views on the nature of the multiplication, with some identifying it as componentwise multiplication and others suggesting it relates to the dot product. The discussion does not reach a consensus on the use of common mathematical operators for this operation.

Contextual Notes

The discussion includes references to specific software (Mathcad and Matlab) and their respective notations, which may not be universally applicable. There is also an implicit assumption regarding the definitions of matrix operations that remains unaddressed.

Who May Find This Useful

Individuals interested in matrix operations, componentwise multiplication, or those working on related homework assignments in mathematics or engineering may find this discussion relevant.

DyslexicHobo
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Hi all,

I need to figure out the mathematical notation to multiply matricies A and B = C so that...

If matrix A is...
a1
a2
a3
a4
a5

and matrix B is...
b1
b2
b3
b4
b5

so that matric C is...
a1*b1
a2*b2
a3*b3
a4*b4
a5*b5

Would this involve using a the transverse of a matrix?

Thanks.
 
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Looks like the componentwise multiplication of vectors to me.
 
That is, the dot product of two vectors.
 
When I calculate the doct product of those two matricies, won't I get a single scalar value?
 
Okay, I found what I was looking for. It's called a Hadamard product. The Hadamard product A and B produces matrix C so that C_i,j = A_i,j * B_i,j.

Is there any way to compute this using common mathematical operators (such as inverse, transpose, dot product, cross product)?

The reason I ask is because I'm doing a homework assignment in Mathcad calculating power requirements of a car at certain speeds. I'm just assigning the speeds to a single-column matrix and the resistant forces to a single-column matrix. I want to output a power matrix.

If I can't figure it out, I'll just have to manually assign a force and velocity variable to each speed, but there must be a way to do this more easily.
 
I don't know what Mathcad is, but in Matlab you would write this sort of multiplication as .* instead of just *. (That last period just ends the sentence of course).
 

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