Spit an array when the value 0 occurs until the value 2

Question

Fabio Taccaliti 2022-6-29

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https://ww2.mathworks.cn/matlabcentral/answers/1750765-spit-an-array-when-the-value-0-occurs-until-the-value-2

评论： Walter Roberson 2022-6-30

I have an array time (6700x1) containing all numbers from -8 to 5 in ascending order.

I would like to have a new array (time_new) based on this that contains all value between 0 and 2.

I know that I can just open the array and look at which position the value 0 occurs and at wich index the value 2 and based on this do time(3981:4962). But since I'm dealing with several arrays where the position of these 2 numbers is not always the same I would like to have something more roboust that I can always use without every time open the array and look for the teo index.

Can someone help to with that?

Thanks in advance

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Dyuman Joshi 2022-6-29

编辑：Dyuman Joshi 2022-6-29

Why do you think finding the position and using the index is not a robust method?

Use logical indexing then. (as @Voss has answered)

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Answer 1

Voss 2022-6-29

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% an array time (6700x1) containing numbers from 
% -8 to 5 in ascending order:
time = linspace(-8,5,6700).'
time = 6700×1
   -8.0000
   -7.9981
   -7.9961
   -7.9942
   -7.9922
   -7.9903
   -7.9884
   -7.9864
   -7.9845
   -7.9825
% time_new based on this that contains 
% all value between 0 and 2:
time_new = time(time >= 0 & time <= 2) % use >, < if you want to exclude 0, 2
time_new = 1031×1
    0.0010
    0.0030
    0.0049
    0.0069
    0.0088
    0.0107
    0.0127
    0.0146
    0.0166
    0.0185

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Fabio Taccaliti 2022-6-30

Exactly, thanks a lot!

Voss 2022-6-30

You're welcome!

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Answer 2

Walter Roberson 2022-6-29

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https://ww2.mathworks.cn/matlabcentral/answers/1750765-spit-an-array-when-the-value-0-occurs-until-the-value-2#answer_996725

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Your request is a bit ambiguous, so I will give two possibilities.

loc0 = find(YourArray == 0, 'first');
%use this
loc2F = find(YourArray == 2, 'first');
subsetF = YourArray(loc0:loc2F-1);
%OR use this
loc2L = find(YourArray == 2, 'last');
subsetL = YourArray(loc0:loc2L);

Now subsetF includes from the first 0 to the last value before the 2. subsetL includes from the first 0 to the last 2. You do not need both of these; I am just not clear which one you want.

Note that this code is not designed to work if there are no 0 or there are no 2.

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Fabio Taccaliti 2022-6-30

Thanks for the answer.

I have this error.

Error using find

Second argument must be a positive scalar integer.

Walter Roberson 2022-6-30

在 MATLAB Online 中打开

loc0 = find(YourArray == 0, 1, 'first');
%use this
loc2F = find(YourArray == 2, 1, 'first');
subsetF = YourArray(loc0:loc2F-1);
%OR use this
loc2L = find(YourArray == 2, 1, 'last');
subsetL = YourArray(loc0:loc2L);