Find and collate matching values.

Hi All,

Lets say I have multiple unique data sets:

data1.gamma = [1,2,3,4,5,6,7,8,9,10];
data1.eta   = [0.1,0.4,0.9,0,0.2,0.5,0.7,0.8,0.9,0.10];
data1.phi ........

data2.gamma = [0,2,0,4,5,9,7,10,9,6];
data2.eta   = [0.1,0.4,0.9,0,0.2,0.5,0.7,0.8,0.9,0.10];
data2.phi ........

and data3, data4 etc as such.

I would like to write a function that can to compare all the data sets and on each data set only keep variable values where

data.gamma

is the same. Any idea how I would go about doing that? I can compare and match 2 data sets. However I am not sure how to compare multiple data sets.

Also I do not know how many data set there will be (data1,data2,data3,data4....). So how do I make the function "scale-up" as necessary. Is that even possible without predefined the variable names?

Any help would be much appreciated.

[Carl]

Hi Abhi. Can you clarify on what you mean by "compare all the data sets and on each data set only keep variable values where data.gamma is the same"? Same in relation to each other, or to some other set of gamma values? For data1 and data2 that you provided, what values do you expect to "keep"?

[OCDER]

https://www.mathworks.com/matlabcentral/answers/360821-compare-and-compile-matching-values-from-various-data-set

Duplicate question?

[Abhi Ove]

Hi it is a duplicate questions. I was not getting any response to the questions, so I posted again hoping to make my question clear-er!

In response to your questions>

I would like to compare gamma values of ALL the data sets. If a single gamma value is present in every data set, I would like to create a database of other variables corresponding to the same gamma value.

Donald has suggested the following which identifies the common variables remarkably well. I am still sort of confused on the last bit.

https://uk.mathworks.com/matlabcentral/answers/360821-compare-and-compile-matching-values-from-various-data-set

[Jos (10584)]

Do *NOT* store your data like this. Use an array of structs.

data(1).gamma = ...
data(2).gamma = ...

[Jos (10584)]

That being said, what is it you want to keep? Can you give a small example of input and required output?

Answer 1

[Image Analyst]

Not sure what "keep" means, but to compare the two arrays, use isequal(). Try this:

if isequal(data1.gamma, data2.gamma)
    % They're equal
else
    % They're not equal.
end

It would be best if your datan were not unique as you said, but a structure array. For example if you had 10 versions of data all with different names you'd have 10*9/2 = 45 separate if blocks to compare all possible pairs. If you had one variable, data, that was a structure array, then you don't need to compare all combinations pair-by-pair, but you could do a nested loop to make all comparisons:

for k1 = 1 : length(data)
    for k2 = 1 : k1-1
        if isequal(data(k1).gamma, data(k2).gamma)
            % They're equal
        else
            % They're not equal.
        end
    end
end

[Abhi Ove]

Thanks a lot for your answer. I have found your advice very helpful. However I have implemented the following method which seems to work wonderfully.

Solution.