How do i count unique elements in two table columns?

Question

ahmed obaid 2017-6-9

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https://ww2.mathworks.cn/matlabcentral/answers/344053-how-do-i-count-unique-elements-in-two-table-columns

评论： ahmed obaid 2017-6-9

采纳的回答： Guillaume

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Dear all;

for the following table:which include student name, class and school name ..

std_name      class       School 
A1              1           Art
A2              1           Art
A3              1           Muc
A4              2           muc
A5              3           Art
A6              2           fun
A7              3           fun
A8              4           Muc
...

i need to count : - how many student in every class, then write new table includes the following result as example: class number and how many student in every class, then names of schools... as shown below:

class     No. of std         School 
1           50               Art, Muc
2           30               muc, fun
3           10               Art, fun
4           100              muc 
etc..
-

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Answer 1

Guillaume 2017-6-9

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https://ww2.mathworks.cn/matlabcentral/answers/344053-how-do-i-count-unique-elements-in-two-table-columns#answer_270167

编辑：Guillaume 2017-6-9

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Simpler, using rowfun which did exist in R2015a:

out = rowfun(@(school) {strjoin(unique(school), ', ')}, A, ...
             'GroupingVariables', 'class', 'InputVariables', 'School')

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ahmed obaid 2017-6-9

thanks a lot for all experiences ...

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Answer 2

Andrei Bobrov 2017-6-9

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https://ww2.mathworks.cn/matlabcentral/answers/344053-how-do-i-count-unique-elements-in-two-table-columns#answer_270153

编辑：Andrei Bobrov 2017-6-9

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A.csv

A = readtable('A.csv');
A.Properties.VariableNames = {'std_name','class','School'};
[g,ii] = findgroups(A.class);
out = table(ii,accumarray(g,1),splitapply(@(x){strjoin(unique(x),',')},A.School,g),...
                                                 'var',{'class','No_of_std','School' });