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comparing two tables or datasets

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gg
gg on 4 Feb 2014
Commented: Peter Perkins on 14 Dec 2017
The question relates to datasets as well as tables. It is stated in the following for datasets only. Assume you have two datasets dsA and dsB, which are of equal dimension with identical variables but are unequal (i.e.
isequal(dsA, dsB)
evaluates "false".
Is there a better way to find the actual row(s) and column(s) (or variable(s)) which are different, than the obvious and tedious one? (Obvious and tedious is to check dimensions, if equal check each variable, apply proper "eq" to each variable)

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Answers (5)

alexandre iolov
alexandre iolov on 23 Jan 2015
Look into setdiff(dsA, dsB),
'''If A and B are tables, then setdiff returns the rows from A that are not in B, with repetitions removed. The rows of table C are in sorted order.'''
however, beware that nan~=nan and similarly for entries of categorical arrays which are undefined. undefined ~= undefined
There might be other gotchas that I don't know of, please share.

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Azzi Abdelmalek
Azzi Abdelmalek on 4 Feb 2014
Edited: Azzi Abdelmalek on 4 Feb 2014
You can access your data then compare them
dsA={1;2;3};
dsA=mat2dataset(dsA);
dsB={1;2;3};
dsB=mat2dataset(dsB)
%compare
sign(dsA.dsA1-dsB.dsB1)

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gg
gg on 4 Feb 2014
I do not think this works for variables where "-" is not defined.
Azzi Abdelmalek
Azzi Abdelmalek on 4 Feb 2014
If you have numeric data, you can use
sign(cell2mat(dsA.dsA1)-cell2mat(dsB.dsB1))

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Sean de Wolski
Sean de Wolski on 4 Feb 2014
Use a for-loop to loop over the variables and test equality:
LastName = {'Smith';'Johnson';'Williams';'Jones';'Brown'};
Age = [38;43;38;40;49];
Height = [71;69;64;67;64];
Weight = [176;163;131;133;119];
BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80];
% Two tables, Height is different
T1 = table(Age,Height,Weight,BloodPressure,...
'RowNames',LastName);
Height = flipud(Height);
T2 = table(Age,Height,Weight,BloodPressure,...
'RowNames',LastName);
props = T2.Properties.VariableNames;
for ii = numel(props):-1:1
eqvars(ii) = isequal(T1.(props{ii}),T2.(props{ii}));
end
Then look at
eqvars
Which will be true everywhere the variables are equal.

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Sean de Wolski
Sean de Wolski on 4 Feb 2014
Then extend it to do that :)
Or use the logical index to extract them after:
T1{:,~eqvars}-T2{:,~eqvars}
gg
gg on 5 Feb 2014
This is (part of) what I mentioned in my question as the "obvious but tedious" solution. I was surprised that objects like table or dataset do not come with an "isequal" method able to handle this. I just wanted to make sure I haven't overlooked something.
Sean de Wolski
Sean de Wolski on 5 Feb 2014
My interpretation is that you want varfun to work like cellfun in that cellfun can work on two cell arrays at once:
C1 = {1, pi, magic(3)}
C2 = {2, pi, magic(3)}
cellfun(@(x,y)x-y,C1,C2,'UniformOutput',false)
Which seems reasonable enough if two tables have all of the same variables..

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Markus Leuthold
Markus Leuthold on 22 May 2015
table1=table(....)
table2=table(....)
%comparison
s1=table2struct(table1)
s2=table2struct(table2)
if isequal(s1,s2)
disp('table1 and table2 are equal')
end
However, I agree there should be an overloaded function isequal in the table class. As a previous commenter already said: If you expect NaN in your table, you have to use
isequaln
instead of
isequal

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Al in St. Louis
Al in St. Louis on 7 Dec 2017
This solution does not work for me. isequaln(t1,t2) yields 0 when the tables are identical without being two pointers to the same table as in your example.
Guillaume
Guillaume on 7 Dec 2017
Can you provide a recipe for that. It seems to work fine for me:
>>t1 = table([1;2;3]);
>>t2 = table([1;2;3]);
>>isequaln(t1, t2)
ans =
1
Peter Perkins
Peter Perkins on 14 Dec 2017
There are no pointers involved in my code, t1 and t2 are completely different instances. Perhaps you have missing values in your tables, in which case you'll probably want to use isequaln.

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Dan
Dan on 27 Feb 2017
isequaln(table1 ,table2) possibly your error derives from the fact that if there are nans isequal will show false.

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