I have two tables. How can I compare the values in the first column of each table, then do a calculation if the values are equal?

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Srh Fwl 2024-2-17

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https://ww2.mathworks.cn/matlabcentral/answers/2083263-i-have-two-tables-how-can-i-compare-the-values-in-the-first-column-of-each-table-then-do-a-calcula

评论： Hassaan 2024-4-14

I imported data from two separate files. The data are stored in two separate tables. Each table contains columns of data. The first column is always "pressure." However, sometimes a particular pressure value is missing from one table. For example, Table 1 might be:

Pressure
1
2
3
4
5

while Table 2 is:

Pressure
1
3
4
5
6

I need to find out when the values in each table are the same (i.e., pressures of 1, 3, 4, and 5). Then I need to do a calculation that uses data from those rows and put the results in a third table.

I cannot figure out how to do this. I have tried:

for i=1:length(Table 2)
    if Table1(i) == Table2(i)
        Table3.append(Table1 .* 0.05) + (Table2 .* 0.95);
    end
end

However, I get the error:

Arrays have incompatible sizes for this operation.

I would be grateful for any advice. Thank you.

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Answer 1

Hassaan 2024-2-17

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https://ww2.mathworks.cn/matlabcentral/answers/2083263-i-have-two-tables-how-can-i-compare-the-values-in-the-first-column-of-each-table-then-do-a-calcula#answer_1410833

编辑：Hassaan 2024-2-17

在 MATLAB Online 中打开

@Srh Fwl A basic idea.

% Example initialization with an additional data column
Table1 = table([1; 2; 3; 4; 5], rand(5, 1), 'VariableNames', {'Pressure', 'DataColumn'});
Table2 = table([1; 3; 4; 5; 6], rand(5, 1), 'VariableNames', {'Pressure', 'DataColumn'});
% Find common 'Pressure' values
commonPressures = intersect(Table1.Pressure, Table2.Pressure);
% Initialize Table3 to store results
Table3 = table([], [], 'VariableNames', {'Pressure', 'Result'});
for i = 1:length(commonPressures)
    % Find rows in each table that match the current pressure
    rowInTable1 = Table1.Pressure == commonPressures(i);
    rowInTable2 = Table2.Pressure == commonPressures(i);
    
    % Use logical indexing to access the 'DataColumn' for calculations
    result = (Table1.DataColumn(rowInTable1) * 0.05) + (Table2.DataColumn(rowInTable2) * 0.95);
    
    % Append the common pressure and result to Table3
    Table3 = [Table3; {commonPressures(i), result}];
end
% Display the result
disp(Table3);
    Pressure    Result 
    ________    _______

       1        0.43724
       3          0.558
       4         0.4823
       5        0.75785

DataColumn Added: The example assumes an additional column named 'DataColumn' exists in both tables for the calculation.

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