if statement for range of array values

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Trader
Trader 2012-5-9
Is there a better way to write this 'if' statement?
for i = 1:size(somevalue)
if (x(i) < xmax && x(i-1) < xmax && x(i-2) < xmax) || (y(i) < ymax && y(i-1) < ymax)
disp('do something');
end
Thanks for your help!
  1 个评论
Oleg Komarov
Oleg Komarov 2012-5-9
Trivial question, do you want the condition to be verified on any (&&) of the 3 consecutive values or on all (&)?

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回答（3 个）

Wayne King
Wayne King 2012-5-9
How about
if (any(x<xmax) || any(y<ymax))
disp('do something');
end
or do you really want to test if every one is? Of course it seems that x<xmax or y<ymax are to be always true.
  4 个评论
显示 2更早的评论
Jan
Jan 2012-5-9
@Sean: This needs to create a temporary array of the length numel(x)+numel(y). Therefore I assume this is slower than Wayne's approach.

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Dr. Seis
Dr. Seis 2012-5-9
I think what you might be after is something like:
if all(x(i-1:i+1) < xmax) || all(y(i-1:i+1) < ymax)
% something
end
  2 个评论
Dr. Seis
Dr. Seis 2012-5-9
Misinterpreted your "if" statement on my previous attempt. This should be what you are after.
Note: "all" will return TRUE if and only if the entire array returned from "x<xmax" is all 1's. "any" will return TRUE if there is one or more 1 in the array returned by "x<xmax".
Richard Brown
Richard Brown 2012-5-9
If doing it this way, the x indices should be i-2:i, and the y indices should be i-1:i, and the loop should start at 3

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Richard Brown
Richard Brown 2012-5-9
To check I've understood correctly, you only want to do something if the current and two preceding x values are all less than xmax, or, the current and preceding y values are both less than ymax. Then, the indices you are interested in are given by:
idx = find(filter([1 1 1], 1, x < xmax) == 3 | filter([1 1], 1, y < ymax) == 2)
Note that 1 and 2 will never appear in idx as your expression cannot be evaluated for these

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