I have a data table containing all sorts of values. It includes these columns:

| Value 1 | Value 2 |
|---------|---------|
|0        |235      |
|1        |123      |
|1        |309      |
|1        |540      |
|2        |34       |
|3        |123      |
|3        |959      |
|3        |3939     |

I want to have a table with Value 2 depending on each value of Value 1. It would look like that:

| Value 1 | Value 2        |
| --------|----------------|
| 0       |[235]           |
|1        |[123, 309, 540] |
|2        |[34]            |
|3        |[123, 959, 3939]|

or something like that.

I've tried several solutions such as:

    t = table;
    for i=1:length(existing_table)  
        t(existing_table, end 1) = existing_table.value2(i) % append to case i
    end;
    
    --> returns Error using  () 
    Right hand side of an assignment into a table must be another table or a cell array.
    
    --------------
    t = table;
    for i=1:length(existing_table)  
        switch existing_table.value2(i) 
            case 0
               t(0, end 1) = existing_table.value2(i) % append to case 
    0
        % etc...
        end;
    end;
    
    
    --> returns Error using  () 
    Right hand side of an assignment into a table must be another table or a cell array.
    --------------

    t = table;
    t.v1 = value1;
    t.v2 = unique(value2) % Does not return the kind of table that I would like

CodePudding user response：

This sounds like a job for accumarray:

% Create sample data
value1 = [0 1 1 1 2 3 3 3].';
value2 = [235 123 309 540 34 123 959 3939].';
T = table(value1,value2);

% Accumarray handles only positive indexes. Get these in idx using unique
[uni,~,idx] = unique(T.value1(:));

% First colum is just the unique value in the first column of T
value1_out = uni;
% accumarray groups the values corresponding to each index. Then @(x) {x}
% gathers it into a cell array
value2_out = accumarray(idx,T.value2,[],@(x) {x});
Tout = table(value1_out,value2_out);