extracting values from a matrix or vector

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Sofia Santos
Sofia Santos 2021-2-17
评论： Image Analyst 2021-2-17
Hi!
I'm new at this and a need a litle help.
How can extract non-consecutive numbers from a vector?
For example, a = [11 22 33 44 55]
I want to extract only the 22 and the 55, b = a (...?...)
thanks

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采纳的回答

Fangjun Jiang
Fangjun Jiang 2021-2-17
b=a([2,5]), second and fifth element

更多回答（1 个）

Image Analyst
Image Analyst 2021-2-17
Consecutive in what way? Consecutive in value or index location? None of those numbers are consecutive in their values. Why those two that you chose? What criteria are you using to decide upon the second and fifth indexes?
% To extract odd numbered indexes:
b = a(1 : 2 : end);
% To extract even numbered indexes:
b = a(2 : 2 : end);
In general you can give "a" a vector of actual indexes, like [2, 4, 5] (this is called linear indexing) OR you can give a vector of logicals (or doubles that can be evaluated as logicals) that is the same size as the array, like [false, true, false, true, true] or [0, 1, 0, 1, 1].
  2 个评论
Sofia Santos
Sofia Santos 2021-2-17
thx!
(there's no critiria, it was just an exemple, i'm still learning the basics)

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