How to compare the values of 2 arrays vs each other?

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ESIDOR PASHAJ
ESIDOR PASHAJ 2018-3-8
评论： Walter Roberson 2024-10-10
Hi guys, I am a bit of a noob at Matlab. What I want to do is compare the values of two arrays with each other to see what % similar are they? So, basically, if I have array A = (1,2,3,4) and array B = (1,2,5,6)...I would like to compare these two to each other using a function or something, and that function should state (in this case) that they are 50% similar. I would appreciate your help.

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njj1
njj1 2018-3-8
What do you mean by "similar"? If you want simply see the number of entries that are the same, then this could do the trick:
s = A==B; %this is a boolean vector that will be 1 if the entries are the same and 0 if different
similarity = sum(s)/numel(s); this is the number of entries that are equal divided by the total number of entries
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njj1
njj1 2018-3-8
I'll try to answer your question as best I can understand it. I'm guessing that you have a for loop in which a variable that is being calculated, and you want to store those calculated variables into a vector for future analysis.
stored_variable = zeros(number_of_computations,1); %pre-allocate for speed
for i=1:number_of_computations
variable1 = i^2 + 2*i + 5; %compute your changing variable here
stored_variable(i) = variable1;
end
You can actually bypass the first computation and go directly to the stored variable like:
stored_variable = zeros(number_of_computations,1); %pre-allocate for speed
for i=1:number_of_computations
stored_variable(i) = i^2 + 2*i + 5; %compute your changing variable here and store it
end
If you have a more specific problem, I might be able to provide a better answer.
ESIDOR PASHAJ
ESIDOR PASHAJ 2018-3-8
I worked around your answer and got to where I wanted to get. Thank you very much.

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更多回答（1 个）

Muhammad Ali
Muhammad Ali 2024-10-10
You can simply use the following code to find at which index both arrays have same values.
Example:
same_index = find(array1 == array2);
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Walter Roberson
Walter Roberson 2024-10-10
This would find locations at which the values were the same, assuming that the two arrays were the same size.
However, the task is to determine " In my example, 1 and 2 appears in both" -- so the order and size of the two arrays can be different.

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