# How to fine a range of values before and after a specific value with a condition

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Laty El 2022 年 2 月 25 日
コメント済み: Star Strider 2022 年 3 月 1 日
Hello,
Hope everyone is fine!
I have an issue regarding the data analysis in Matlab, if someone could support me.
I have a table of different columns (datetime, VAR1 and VAR2). I need to:
- first find a specific value of VAR1 (eg. X=5)
- then find a range of values of VAR2 before and after X, according to the values of VAR1 equal to 0.
I need to find something like that:
Datetime VAR1 VAR2
... 0 y1
... 0 y2
... 0 y3
... 0 y4
... 5 y5
... 0 y6
... 0 y7
... 0 y8
... 0 y9
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Laty El 2022 年 2 月 25 日
@_ For my case i need to find many 0 rows before and after, and i have to use the same number of rows (before and after).

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### 採用された回答

Star Strider 2022 年 2 月 25 日
Try this —
GetRange = @(range,Val,T,Col) strfind(T{:,Col}', [zeros(1,range) Val zeros(1,range)]);
Col2 = zeros(24,1);
Col2(randi(24,24,1)==5) = 5;
Table = table(datetime('now')+hours(0:23).', Col2, rand(24,1), 'VariableNames',{'Datetime','VAR1','VAR2'})
Table = 24×3 table
Datetime VAR1 VAR2 ____________________ ____ ________ 25-Feb-2022 14:16:05 0 0.94761 25-Feb-2022 15:16:05 0 0.66998 25-Feb-2022 16:16:05 0 0.80789 25-Feb-2022 17:16:05 0 0.39264 25-Feb-2022 18:16:05 0 0.28526 25-Feb-2022 19:16:05 0 0.29068 25-Feb-2022 20:16:05 0 0.44018 25-Feb-2022 21:16:05 0 0.85058 25-Feb-2022 22:16:05 5 0.50154 25-Feb-2022 23:16:05 0 0.11087 26-Feb-2022 00:16:05 5 0.68359 26-Feb-2022 01:16:05 0 0.80208 26-Feb-2022 02:16:05 0 0.053463 26-Feb-2022 03:16:05 0 0.98176 26-Feb-2022 04:16:05 0 0.69536 26-Feb-2022 05:16:05 0 0.61461
idx = find(Table.VAR1 == 5)
idx = 3×1
9 11 20
range = 3;
start = GetRange(3,5,Table,2)
start = 17
for k = 1:numel(start)
Out{k,:} = Table(start(k) : start(k)+range*2,:);
end
Out{:}
ans = 7×3 table
Datetime VAR1 VAR2 ____________________ ____ ________ 26-Feb-2022 06:16:05 0 0.11047 26-Feb-2022 07:16:05 0 0.11028 26-Feb-2022 08:16:05 0 0.81538 26-Feb-2022 09:16:05 5 0.96058 26-Feb-2022 10:16:05 0 0.97877 26-Feb-2022 11:16:05 0 0.025627 26-Feb-2022 12:16:05 0 0.48768
It will only detect and return regions with a centre value of 5 (in this example) and zeros within the specified range. So here, it does not return the values at 9 and 11 because they do not meet the criteria, and it does return the value with the centre value at 20 because it meets the criteria.
The ‘GetRange’ function arguments are ‘range’ the range to consider, here 3, ‘Val’ the value to compare (here 5), ‘T’ the table variable name (here ‘Table’), and ‘Col’ the column to test (here 2).
.
##### 18 件のコメント17 件の古いコメントを表示17 件の古いコメントを非表示
Star Strider 2022 年 3 月 1 日
As always, my pleasure!

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