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

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];

Answer 1

[Sameer]

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!

[Andrew Sol]

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]

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];

Answer 2

[Image Analyst]

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