How to use the dot product within a loop to multiply a series of rows?!

Question

Joshua Otter 2014-3-24

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/122929-how-to-use-the-dot-product-within-a-loop-to-multiply-a-series-of-rows

回答： James Tursa 2014-3-25

采纳的回答： Gareth Thomas

在 MATLAB Online 中打开

I currently have two matrices.

- V = (1*3) matrix

- coordNORMALS = (18766*3) matrix.

I would like to take the dot product of the two such that:

- C = dot ( V, coordNORMALS)

I understand that to take the dot product the size of the two matrices must be equal, however I would like to find C for each row, i.e get 18766 values of C

C = dot ( V, coordNORMALS (1 , : )) all the way to C = dot ( V, coordNORMALS ( end , : ))

I have tried to use a loop in the following format but end up in an infinite loop:

for i=1:length(coordNORMALS)
  C(i) = dot(V,coordNORMALS(i,:))
end
end

If anyone knows how to help, please reply

Many Thanks Josh

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Answer 1

Gareth Thomas 2014-3-24

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/122929-how-to-use-the-dot-product-within-a-loop-to-multiply-a-series-of-rows#answer_130129

在 MATLAB Online 中打开

V = rand(1,3)
C = rand(13,3)
dot(V,C(1,:))
dot(V,C(2,:))
for i = 1:length(C)
   d(i) = dot(V,C(i,:));
end

Does this not work?

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Joshua Otter 2014-3-24

It works fine, just me being an idiot. I had the answers coming up in the command window which took ages to load so I thought I was stuck in an infinite loop. Thanks Gareth.

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