Create new column in table from data across multiple columns

I have a table with multiple events (P1, P2, N1, early P3, P3) listed in one column, ROI. There are several adjacent columns with latencies that have the same events in their titles. I would like to create a new column (Latencies) with the latencies in the adjacent columns extracted and matched the events in the ROI column. For example if the event under ROI is P1 then under the new column, Latencies, the data in the same row under P1_Max_Lat would be copied. I attached a sample table.

Answer 1

[Image Analyst]

Try this:

load('Example_table.mat')
[rows, columns] = size(sampletable)
tLatencies = table(zeros(rows, 1), 'VariableNames', {'Latencies'})
newTable = [sampletable, tLatencies]
for row = 1 : rows
    % Get the event name.
    event = newTable.ROI{row}
    % Based on that, get the name of the column 
    % we need to look for to get the data.
    columnName = sprintf('%s_Max_Lat', event)
    % If that column is there, copy the number to the Latencies column.
    if ismember(columnName, newTable.Properties.VariableNames)
        % Get data from the appropriate column.
        data = newTable.(columnName)(row)
        % Put data into the latencies column
        newTable.Latencies(row) = data;
    else
        fprintf('There is no column called %s in the table.\n', columnName);
    end
end

[DavidL88]

This is great thak you. The N1 events are coming back 0. The title is Min for this column. Is there a way to add an OR type statement to the line with sprintf? The other events are being matched accuartely.

[Image Analyst]

Sure. I understand better now what you want and below is a more robust version that finds the first column that starts with the event string:

load('Example_table.mat')
[rows, columns] = size(sampletable);
tLatencies = table(zeros(rows, 1), 'VariableNames', {'Latencies'});
newTable = [sampletable, tLatencies];
[rows, columns] = size(newTable); % Update size.
variableNames = newTable.Properties.VariableNames;
for row = 1 : rows
    % Get the event name.
    event = newTable.ROI{row};
    % Based on that, get the name of the column 
    % we need to look for to get the data.
    foundIt = false;
    for col = 1 : columns
        if startsWith(variableNames{col}, event)
            % Indicate that we found a column name that starts with the event name.
            foundIt = true;
            columnName = variableNames{col};
            break;
        end
    end
    if ~foundIt
        % We did not find any column starting with the event name.
        fprintf('There is no column starting with %s in the table.\n', event);
        continue; % Skip the rest of the loop for this iteration only.
    end
    % If that column is there, copy the number to the Latencies column.
    if ismember(columnName, newTable.Properties.VariableNames)
        % Get data from the appropriate column.
        data = newTable.(columnName)(row);
        % Put data into the latencies column
        newTable.Latencies(row) = data;
    end
end
% Report the new table to the command window:
newTable

If this works, please "Accept this Answer". Thanks in advance. If not, let me know what row is bad.

[DavidL88]

Worked perfectly. Thank you.