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

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Jordan David
Jordan David 2023-2-15
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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VBBV
VBBV 2023-2-15
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.
  2 个评论
Kenneth Louis
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.

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更多回答（2 个）

Jai Khurana
Jai Khurana 2023-2-15
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.
Oguz Kaan Hancioglu
Ran in:
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
100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100

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