MATLAB: How to find the total value by category in a table

categoryMATLABStatistics and Machine Learning Toolbox

Best Answer

G = findgroups(Table.Clase);
Result = splitapply(@sum,Table.Monto,G);
Result = table(categories(Table.Clase),Result,'VariableNames',{'Clase','Monto'})

Related Solutions

MATLAB: Problem Using groupsummary function

The error message tells you the problem:

A grouping variable of class 'table' is not supported.

This line,

zt=table(table1,table2,'VariableNames',{'xc','yc'});

combines two tables. zt.xc is a table within the zt table. Same with zt.yc.

The grouping variable cannot be a table.

If table1 and table2 are tables with a single column and an equal number of rows, you can combine them horizontally like this.

zt = [table1, table2];

You can change the variable names before or after combing the table columns.

If those tables do not have single columns, you can continue with your current method but you'll need to specify the grouping column differently.

MATLAB: How to sum over grouped data in a table

For MATLAB R2018b and later:

If you only require a summary table containing the sum for each group, use "groupsummary".

>> G = groupsummary(exampletable,'groups','sum')
G =
  3×3 table
    groups    GroupCount    sum_values
    ______    __________    __________
     'a'          2              3    
     'b'          2              7    
     'c'          2             11

Use "grouptransform" to both perform the sum calculation by group and expand the result back to your original "exampletable".

>> exampletable = grouptransform(exampletable,'groups',@sum,'ReplaceValues',false)
exampletable =
  6×3 table
    groups    values    fun_values
    ______    ______    __________
     'a'        1            3    
     'a'        2            3    
     'b'        3            7    
     'b'        4            7    
     'c'        5           11    
     'c'        6           11

The documentation pages for "groupsummary" and "grouptransform" are below.

https://www.mathworks.com/help/matlab/ref/double.groupsummary.html

https://www.mathworks.com/help/matlab/ref/double.grouptransform.html

For MATLAB R2018a and earlier:

You can use a for loop to calculate the sums in a new, preallocated vector. Then, append this vector to the end of your original table.

y = zeros(size(groups));
for i = 1:length(groups)
    y(i) = sum(values(ismember(groups,groups(i))));
end
exampletable.sum_values = y;

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Related Solutions

MATLAB: Problem Using groupsummary function

MATLAB: How to sum over grouped data in a table

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