Possible to iterate over table rows without a loop index variable?

Question

Leon 2024-4-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2108686-possible-to-iterate-over-table-rows-without-a-loop-index-variable

编辑： Leon 2024-4-21

To iterate over the variables (columns) of a table, you can do this:

my_table = table([1; 2; 3], [4; 5; 6], ["Seven"; "Eight"; "Nine"])
my_table = 3x3 table
    Var1    Var2     Var3  
    ____    ____    _______

     1       4      "Seven"
     2       5      "Eight"
     3       6      "Nine" 
for var = my_table
    disp(var)
end
    Var1
    ____

     1  
     2  
     3  

    Var2
    ____

     4  
     5  
     6  

     Var3  
    _______

    "Seven"
    "Eight"
    "Nine" 

Is there a way to adjust this to operate on each row without using an index variable? Using a loop index variable, as follows, works fine but is a bit less elegant than the column-by-column solution.

for row_index = 1:height(my_table)
    row = my_table(row_index, :);
    disp(row)
end
    Var1    Var2     Var3  
    ____    ____    _______

     1       4      "Seven"

    Var1    Var2     Var3  
    ____    ____    _______

     2       5      "Eight"

    Var1    Var2     Var3 
    ____    ____    ______

     3       6      "Nine"

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Torsten 2024-4-18

"rows2vars" transposes your table, if it is that what you want to achieve.

Leon 2024-4-21

编辑：Leon 2024-4-21

Thanks. It's useful to know about but I want to get one table row each time, that I can index by the variable name, to be robust to changes in variable order and new variables in the future, whereas with rows2vars I would get a cell array (since the table variables are of different types) and have to index by number. Presumably it's also a bit inefficient converting to cells and using them, though that doesn't matter for my current use case since there is a lot of other processing per loop.

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Answer 1

Steven Lord 2024-4-18

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2108686-possible-to-iterate-over-table-rows-without-a-loop-index-variable#answer_1443946

To perform an operation on all rows of a table array you could use rowfun, but that isn't the same as writing a general for loop. I'd personally probably just use the for loop over 1:height(theTableArray).

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Bruno Luong 2024-4-18

编辑：Bruno Luong 2024-4-18

Some authority suggests using rowfun on table instead of for-loop row indexing if runtime performance matters.

https://www.mathworks.com/matlabcentral/discussions/general/847971-what-frustrates-you-about-matlab-2/2562386

Read the comments following my complain about combinations only providee table as output format.

Transpose the table as Torsen suggets or retreive the content of the table (without the tanle container) are two other work around of performance hi issue.

Leon 2024-4-21

编辑：Leon 2024-4-21

Interesting to know about for if I need more perfomance. I think I will just stick with having an index since I have a lot more processing in each loop, and want to be able to index by name for future-proofing if variables are added or order changed. Thanks

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