comparing two tables or datasets
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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)
回答（5 个）
alexandre iolov
2015-1-23
6 个投票
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.
Azzi Abdelmalek
2014-2-4
编辑：Azzi Abdelmalek
2014-2-4
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)
2 个评论
gg
2014-2-4
Azzi Abdelmalek
2014-2-4
If you have numeric data, you can use
sign(cell2mat(dsA.dsA1)-cell2mat(dsB.dsB1))
Sean de Wolski
2014-2-4
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.
4 个评论
gg
2014-2-4
Sean de Wolski
2014-2-4
Then extend it to do that :)
Or use the logical index to extract them after:
T1{:,~eqvars}-T2{:,~eqvars}
gg
2014-2-5
Sean de Wolski
2014-2-5
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..
Markus Leuthold
2015-5-22
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
4 个评论
Peter Perkins
2015-5-26
The isequal function already works on tables, so you don't need to convert to structs:
>> t1 = array2table(randn(5,3));
>> t2 = t1;
>> isequal(t2,t1)
ans =
1
>> t2.Var1(1) = 0;
>> isequal(t2,t1)
ans =
0
The original question was, "how to find what part of them is not equal?", for which setdiff/xsetxor, or some of the other posted solutions, will work.
Al in St. Louis
2017-12-7
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
2017-12-7
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
2017-12-14
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.
Dan
2017-2-27
0 个投票
isequaln(table1 ,table2) possibly your error derives from the fact that if there are nans isequal will show false.
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