How to sortrows by specific strings

Question

David Rodriguez 2021-3-9

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/767877-how-to-sortrows-by-specific-strings

编辑： David Rodriguez 2023-1-14

I am making, an attendance sheet for a college club meeting. I have a table filled with names (string) and would like to sort them by their position (string).

I want to sort the list of people who sign in at the end of the meeting by their held "position."

1. Officers would appear at the top of the list

2. Members next

3. Guests last

However I am struggling to use sort or sortrows to do this, so there must be other commands that I could try. I provided example code and a desired output to better illustrate my question.

For example

% Create Data
Position = {'Vice President';'Guest';'Member';'President'};
Name = {'John';'Jane';'Nancy';'Bob'};
% Turn data into a table
data = table(Position,Name); 
% Sort names by position:
% President->VP->Member->Guest
%%%% Your Helpful Advice would go here :) %%%%

Desired Output

%{
data =
  4×2 table
         Position           Name   
    __________________    _________
    {'President'     }    {'John' }
    {'Vice President'}    {'Jane' }
    {'Member'        }    {'Nancy'}
    {'Guest'         }    {'Bob'  }
%}

Any suggestions are appreciated, thank you!

Updated to make question easier to understand for others.

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Answer 1

Steven Lord 2021-3-10

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https://ww2.mathworks.cn/matlabcentral/answers/767877-how-to-sortrows-by-specific-strings#answer_643682

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desired_order = {'President','Vice President','Member','Guest'};
Position = {'Vice President';'Guest';'Member';'President'};
Name = {'John';'Jane';'Nancy';'Bob'};

Turn the Position variable into a categorical array whose order matters (the array is an ordinal array.) The ordering is given by the desired_order list.

ranks = categorical(Position, desired_order, 'ordinal', true)
ranks = 4×1 categorical array
     Vice President 
     Guest 
     Member 
     President 

Store the data in a table array.

results = table(ranks, Name, 'VariableNames', ["Rank", "Name"])
results = 4x2 table
         Rank           Name   
    ______________    _________

    Vice President    {'John' }
    Guest             {'Jane' }
    Member            {'Nancy'}
    President         {'Bob'  }

Sort the table by Rank (taking advantage of the fact that it is ordinal.)

results = sortrows(results, "Rank")
results = 4x2 table
         Rank           Name   
    ______________    _________

    President         {'Bob'  }
    Vice President    {'John' }
    Member            {'Nancy'}
    Guest             {'Jane' }

Who's the Member?

results{results.Rank == 'Member', 'Name'}
ans = 1x1 cell array
    {'Nancy'}

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David Rodriguez 2021-3-10

编辑：David Rodriguez 2021-3-10

Ahh, I did not know about categorical, I will certainly read the documentation on it.

Thank you so much for your time and help!! This was a smaller version of what I am dealing with and your code runs about 25-30% faster with this small amount of data, so I bet when I implement it into my actual data set, it will be much faster. And thank you for explaining the code, with output, really helpful!

Thien-Minh 2022-11-20

perfect!

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Answer 2

David Rodriguez 2021-3-9

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/767877-how-to-sortrows-by-specific-strings#answer_643582

编辑：David Rodriguez 2021-3-10

在 MATLAB Online 中打开

After working on this much longer, this is what I came up with, but am wondering if there is a better way of solving the problem.

%% Sort Rows by President->Vp->Member->Guest
% turn data into cells
data = table2cell(data);
% Create new column
new_col = zeros(length(data),1);
% Write the desired order
desired_order = {'President','Vice President','Member','Guest'};
n_positions = length(desired_order);
% Assign ranking to each position
%{
P - 1
VP - 2
M - 3
G - 4
%}
% Create a "Ranking" vector for each position
ranking = 1:n_positions;
% Assign appropiate value in the new column
for aa = 1:n_positions
    position = desired_order(aa);
    position_check = find(strcmp(data(:,1),desired_order(aa)));
    new_col(position_check) = ranking(aa);
end
% add col, sort the data, remove that col
data = addvars(cell2table(data),new_col);
data = sortrows(data,'new_col','ascend');
data = removevars(data,width(data));