How to write a product of two numbers 6 and 7 in Matlab code to get 42

I have forgotten how to write a numbers product. What is the multiplication symbol in Matlab?

If I want to get 42, how do I write '6 "times what symbol" 7' on a Matlab command line? A simple dot . between them does not work and neither does an x.

So does anyone ever multiply simple numbers such as '1,087 $' "times" 1.08 percent' for finding out credit card costs ? In Matlab code.

Thanks

I have looked through the Documentation and there is no such simple question or answer.

Answer 1

[Walter Roberson]

times(6,7)

ans = 42

[Frank Uhlig]

Nice answer. So multiplying two numbers needs the 'times' command in front of the two numbers. How to multiply 6 numbers tom get their product? How about multiplying all number entries of a 10 by 11 matrix together? That would take a doo0000zens of lines of code. BAD ! Or am I too dumb to see a better way ... ?

But for matrix multiplications, then the * could create the product of two 1 by 1 matrices. And it would take a couple of 'reshape' commands ... to switch from the umber realm to matrix realm and back. ... ? ? ?? ...

How about creating 1 by 1 matrices for each of the numbers and then multiplying these number matrices via * ?

I did not realize, Matlab was running so confusingly. Why I wonder, Cleve and the computation experts at Mathworks ... , why, oh "WHY" ?

What would the number of code statement be to multiply 20 matrices of compatible sizes together? How about 200 such matrices? Coding for a week, it seems and no results until all lines of code are flawlessly written down on a page + of commnands.

There must be simpler way, I bet. Any answers?

Thanks,

FrankU

And the Matlab Documentations do not mention any such 'mundane' task of simple multiplications at all.

[Stephen23]

"So multiplying two numbers needs the 'times' command in front of the two numbers"

No, that is just one way to multiply two numbers.

"How to multiply 6 numbers tom get their product? How about multiplying all number entries of a 10 by 11 matrix together? That would take a doo0000zens of lines of code. BAD ! Or am I too dumb to see a better way ... ?"

https://www.mathworks.com/help/matlab/ref/double.prod.html

"And the Matlab Documentations do not mention any such 'mundane' task of simple multiplications at all."

https://www.mathworks.com/help/matlab/ref/double.times.html

https://www.mathworks.com/help/matlab/matlab_prog/matlab-operators-and-special-characters.html

The Getting Started tutorials also introduce matrix multiplication:

https://www.mathworks.com/help/matlab/learn_matlab/matrices-and-arrays.html

"How about creating 1 by 1 matrices for each of the numbers and then multiplying these number matrices via * ? "

Use matrices instead.

[Steven Lord]

Nice answer. So multiplying two numbers needs the 'times' command in front of the two numbers. How to multiply 6 numbers tom get their product?

Mutiplying numbers requires calling the times function or using the * or .* operators. For the question you asked here, use the prod function.

x = [1 2 3 4 5 6];
y = prod(x) % 6! or factorial(6) for this specific x vector

y = 720

How about multiplying all number entries of a 10 by 11 matrix together? That would take a doo0000zens of lines of code. BAD ! Or am I too dumb to see a better way ... ?

That's prod as well, as long as you tell it to take the product over all the dimensions.

x = randi(5, 10, 11) % Sample matrix with random integers between 1 and 5

x = 10×11

1 4 3 1 4 2 1 2 5 4 3 3 5 5 5 1 5 1 2 5 4 1 5 2 5 2 2 3 3 3 5 1 4 3 4 1 5 1 5 2 3 4 3 1 4 1 1 3 5 2 4 3 4 1 5 2 4 3 2 3 5 2 5 1 2 1 1 4 2 2 3 2 3 1 3 3 2 1 2 5 3 4 2 3 2 4 3 5 4 1 3 1 3 3 2 5 1 5 1 3 4 1 2 5 3 3 1 3 1 2

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y = prod(x, "all")

y = 1.3101e+43

But for matrix multiplications, then the * could create the product of two 1 by 1 matrices.

It does.

And it would take a couple of 'reshape' commands ... to switch from the umber realm to matrix realm and back. ... ? ? ?? ...

I assume "umber" is a typo for "number". I think you're drawing a distinction between scalar values (plain numbers) and matrices. MATLAB doesn't make that distinction; a scalar value is a matrix.

ismatrix(42)

ans = logical
   1

How about creating 1 by 1 matrices for each of the numbers and then multiplying these number matrices via * ?

For scalars, matrix multiplication (with the * operator) and element-wise multiplication (with the .* operator) are the same.

x1 = 6*7

x1 = 42

x2 = 6.*7

x2 = 42

I did not realize, Matlab was running so confusingly. Why I wonder, Cleve and the computation experts at Mathworks ... , why, oh "WHY" ?

What would the number of code statement be to multiply 20 matrices of compatible sizes together? How about 200 such matrices? Coding for a week, it seems and no results until all lines of code are flawlessly written down on a page + of commnands.

If you're creating 20 or 200 individual matrices, that's a sign that you're likely creating variables with numbered names (x1, x2, x3, ...) Can you do that? Yes. Should you do that? The general consensus is no.

If you wanted to multiply those individual matrices element-wise, I would store them in a 3-dimensional array and then use prod with a dimension input argument. In the example below, the answer ought to be [1*5, 2*6; 3*7, 4*8] or [5, 12; 21, 32]

x = cat(3, [1 2; 3 4], [5 6; 7 8])

x = 
x(:,:,1) =

     1     2
     3     4


x(:,:,2) =

     5     6
     7     8

y = prod(x, 3) % Take the product in dimension 3

y = 2×2

5 12 21 32

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And the Matlab Documentations do not mention any such 'mundane' task of simple multiplications at all.

Searching the MATLAB documentation for "multiply" gives an AI answer that references the two multiplication operators. I note that the pages in the documentation for MATLAB don't show up until page 5 of the raw search results; if you post what you searched for I could pass that along to the documentation staff to see if they can make the MATLAB results show up earlier.

If you opened the documentation itself, the second page of the Get Started with MATLAB documentation talks about matrix and element-wise multiplication. The Language Fundamentals category also includes a sub-category Operators and Elementary Operations that talks about Arithmetic Operations.

So the documentation does discuss "simple multiplications".

Since you seem like you're a new(ish) user of MATLAB, I suggest you start with the free MATLAB Onramp tutorial to quickly learn the essentials of MATLAB.

[Walter Roberson]

times(6,7) is the formal internal operation for 6 .* 7 -- that is, 6 .* 7 is internally rewritten into times(6,7). (This has some implications for overloading operators: you can overload the .* operator by overloading the times function.)

mtimes(6,7) is the formal internal operation for 6 * 7 .

The times operator is element-by-element multiplication.

The mtimes operator is algebraic matrix multiplication.

If you happen to * between a matrix and a scalar, then it "devolves" into an internal .* operation.

Answer 2

[DGM]

You mean like

p = 6*7

p = 42

p = 1087*1.08/100

p = 11.7396

See also:

https://www.mathworks.com/help/matlab/arithmetic-operators.html (unroll the sections to see the hidden links)

https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

Answer 3

[Image Analyst]

Did you try getting help on multiplication? For simple multiplication it's simply * like it is in every other language I've used

p = 6 * 7

p = 42

For other kinds of multiplication, see the list below:

help multiplication

--- multiplication not found. Showing related topics. ---

conv                           - Convolution and polynomial multiplication
pagemtimes                     - Page-wise matrix multiplication
double.mtimes                  - Matrix multiplication
.*                             - Multiplication
jc_0610: Operator order for multiplication and division block - 
jc_0611: Input sign for multiplication and division blocks - 
Use floating-point multiplication to handle net slope corrections - Net slope correction computation for floating-point to fixed-point casts
gmultiply                      - Generalized multiplication
nnet.cnn.layer.MultiplicationLayer - Multiplication layer
conv                           - Convolution and polynomial multiplication of fi objects
pow2                           - Efficient fixed-point multiplication by 2^{K}
quaternion.mtimes              - Quaternion multiplication
.*                             - Element-wise quaternion multiplication
linearArray.patternMultiply    - Radiation pattern of array using pattern multiplication
quaternion.mtimes              - Quaternion multiplication
.*                             - Element-wise quaternion multiplication
.*                             - Element-by-element multiplication of fi objects
quaternion.mtimes              - Quaternion multiplication
.*                             - Element-wise quaternion multiplication
se2.mtimes                     - Transformation or rotation multiplication

    Search the documentation for multiplication
       docsearch multiplication