Multiply Individual Cells of a Matrix by a Scalar Using a For Loop

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Jordan David 2023-2-15

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评论： Jordan David 2023-2-23

I have a simple conversion problem where I have a matrix of pressure data (say p1) in hectopascals and need to convert the data to pascals by multiplying the individual elements by the scalar 100. While I understand this is as simple as multiplying the matrix variable by 100 (p1*100), I'm suppose to use a for loop to achieve this.

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Answer 1

VBBV 2023-2-15

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p1 = rand(100,1);% pressure matrix
for k = 1: length(p1)
P1(k) = p1(k)*100;
end

In this case, The previous solutions are certainly better compared to using a for loop however, if you are suppose to use a for loop then you can achieve it as above.

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Kenneth Louis 2023-2-15

I'm in the same class as the poster. Our instructor gave us a large matrix of data 96 x 144 cells and he wants us to use a for loop to convert the entire matrix into another matrix of the same demensions with all of the data multiplied by 100.

I am very sorry for the (potentially stupid) follow-up question, but how are we to get the output matrix to have the same demensions and have each individual cell multiplied by the scalar?

further, why doesn't the simple code

for x = p1

p1_output= x*100

end

work if p1 is the matrix in question? When I run this code, it only posts one column of output instead of all 144.

Jordan David 2023-2-23

Thank you!

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Answer 2

Jai Khurana 2023-2-15

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You can use the .* operator to perform element-wise multiplication between a matrix and a scalar. For example, to multiply each element of matrix p1 by a scalar value 100, you can write:

100 .* p1

This will create a new matrix with the same dimensions as A, where each element of p1 is multiplied by 100.

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Answer 3

Oguz Kaan Hancioglu 2023-2-15

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You can elimnate for loop by using element wise multiplication in Matlab.

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

If you multiply the matrix with the scalar value * operator multiply all elements of the matrix using the same scalar.

pascal = 100*ones(5,5)
pascal = 5×5
 100   100   100   100
 100   100   100   100
 100   100   100   100
 100   100   100   100
 100   100   100   100