dot in an expression

2021 4 15
1 个回答
更新时间：2021 4 15
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Hi guys. What does the dot in sinc(x) = sin(x)./x do? Remove a singularity or what?

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David Fletcher
David Fletcher 2021-4-15
编辑：David Fletcher 2021-4-15

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Element by element division

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Robert Bag
Robert Bag 2021-4-15
but why do I not need in for instance sin(x)? isnt it already understood that this is not a matrix?
David Fletcher
David Fletcher 2021-4-15
编辑：David Fletcher 2021-4-15
It could be a matrix - if you applied the sin function and x was a matrix it would apply sin(x) to each value in the matrix, but the way sin is applied is not fundamentally different whether x is a scaler, a vector, or a matrix, whereas x.*y is a fundamentally different method of application than x*y (element by element multiplication as opposed to matrix multiplication). In your example the dot indicates element by element division as opposed to matrix right division which is used to solve linear equations
Robert Bag
Robert Bag 2021-4-15
Thanks a lot. But why do i especially need it for sin(x)/x? I get an error when i but it without a dot. I thought it had stg to do with that it is not defined on x = 0?
Robert Bag
Robert Bag 2021-4-15
Ok read now.thnx
Adam Danz
Adam Danz 2021-4-15
编辑：Adam Danz 2021-4-15
Ran in:
Ran in:
Compare the following
x = magic(3)
x = 3×3
8 1 6 3 5 7 4 9 2
sin(x)/x % matrix division
ans = 3×3
0.0997 -0.1770 0.1807 0.0666 0.0824 -0.1597 -0.1543 0.2902 -0.0983
sin(x)./x % element-wise division
ans = 3×3
0.1237 0.8415 -0.0466 0.0470 -0.1918 0.0939 -0.1892 0.0458 0.4546
Additional reference: https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

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Robert Bag
Robert Bag
2021-4-15

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Adam Danz
Adam Danz
2021-4-15

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