x = j:i:k creates a regularly-spaced vector x using i as the increment between elements. What about x = j:i:k:m? or j:i:k:m:n?

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Guilherme Silva 2018-2-23

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https://ww2.mathworks.cn/matlabcentral/answers/384323-x-j-i-k-creates-a-regularly-spaced-vector-x-using-i-as-the-increment-between-elements-what-about

编辑： James Tursa 2018-2-23

I hope I am clear enough. I think it is very odd that this works with how many elements you want to separate with colons. It appears to disregard any elements in between the first and last.

This doesn't appear in the documentation.

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Answer 1

James Tursa 2018-2-23

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编辑：James Tursa 2018-2-23

在 MATLAB Online 中打开

This is simply left-to-right operator evaluation.

j:i:k:m:n

evaluates as

(j:i:k):m:n

And, as stated in the doc:

"If you specify nonscalar arrays, then MATLAB interprets j:i:k as j(1):i(1):k(1)."

So your syntax, although probably confusing, is covered in the doc and simply uses the first element of the created vectors at each intermediate result when generating the next intermediate result.

EDITED to delete comments that didn't apply

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Guilherme Silva 2018-2-23

在 MATLAB Online 中打开

I think it actually does evaluate as

(j:i:k):m:n

e.g.

1:2:3:4:5
ans =
      1   5
(1:2:3):4:5
ans = 
      1   5

So it gets the first two colons, evaluates them and then uses the first element of the generated vector for the next two colons evaluation? It gets really confusing. Thanks for your answer.

James Tursa 2018-2-23

编辑：James Tursa 2018-2-23

You're right. I was using 1:2:3:4 as one of the test cases for my spot testing, but that doesn't match your five element pattern so that part of my answer didn't apply. I have edited my answer.

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