Finding a pattern in a table and the coordinates of the "first hit"

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Andrew Sol
Andrew Sol 2024-11-14，10:24
回答： Image Analyst 2024-11-14，15:16
I have a table like this:
'NaN' NaN NaN
'NaN' NaN NaN
'NaN' NaN NaN
'07:02:58.830' 1 NaN
'07:02:58.830' 1 831
'07:02:58.830' 1 NaN
'07:02:58.830' 1 NaN
'07:02:58.830' 1 831
'NaN' NaN NaN
'07:02:59.430' 2 NaN
'07:02:59.430' 2 831
'07:02:59.430' 2 819
'07:02:59.430' 2 819
The first column contains the time in the format X:Y:Z.
What I need: I need to find this pattern in the first column and calculate the coordinates of the first hit.
What the result should look like: in the case of the table in question, the result should be the coordinate of the cell in which this pattern occurs for the first time. In this case, it is [row,col] = [4,1];

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回答（2 个）

Sameer
Sameer 2024-11-14，10:53
编辑：Sameer 2024-11-14，10:56
Ran in:
Hi @Andrew Sol
To find the first occurrence of a specific pattern in the first column of your table you can create a duration object from a time string ('07:02:58.830') and search for its first occurrence in table's first column using find
Here's how you can do it:
load('Table.mat');
pattern = duration('07:02:58.830', 'Format', 'hh:mm:ss.SSS');
firstColumn = Table{:, 1};
% Find the index of the first occurrence of the pattern
index = find(firstColumn == pattern, 1);
if ~isempty(index)
fprintf('The first occurrence of the pattern is at [row, col] = [%d, %d];\n', index, 1);
else
fprintf('Pattern not found.\n');
end
The first occurrence of the pattern is at [row, col] = [4, 1];
Please refer to below MathWorks documentation links:
https://www.mathworks.com/help/releases/R2024a/matlab/ref/duration.html
https://www.mathworks.com/help/releases/R2024a/matlab/ref/find.html
Hope this helps!
  2 个评论
Andrew Sol
Andrew Sol 2024-11-14，11:04
编辑：Andrew Sol 2024-11-14，11:05
Thank you for your answer! And if the time is unknown in advance and you I to find a time pattern (the time can be any, the main thing is that it is in the format 'hh:mm:ss.SSS'), how will the code change?
In other words: how to find the first occurrence of an arbitrary time of a given format in a table?
Sameer
Sameer 2024-11-14，11:57
Ran in:
load('Table.mat');
firstColumnStr = cellstr(Table{:, 1});
timePattern = '\d{2}:\d{2}:\d{2}\.\d{3}';
index = find(~cellfun('isempty', regexp(firstColumnStr, timePattern)), 1);
if ~isempty(index)
fprintf('The first occurrence of the time pattern is at [row, col] = [%d, %d];\n', index, 1);
else
fprintf('Time pattern not found.\n');
end
The first occurrence of the time pattern is at [row, col] = [4, 1];

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Image Analyst
Image Analyst 2024-11-14，15:16
Ran in:
Another way is to use ismember
% Load data from .mat file.
S = load('Andrew Table.mat');
t = S.Table;
% Extract first column into it's own variable (optional - just for convenience).
times = t{:, 1}; % This variable is of type "duration".
% Define the pattern we are trying to find
pattern = duration([07,02,58.830])
pattern = duration
07:02:58
% Find the first row where it occurs
[~, matchingRow] = ismember(pattern, times)
matchingRow = 4

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