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calculation of a mean matrix

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Subrat kumar sahoo
Subrat kumar sahoo am 15 Aug. 2012
Kommentiert: Steven Lord am 25 Apr. 2023
Hi I have two matrices
a = [1 2 3; 2 3 4]
and
b = [2 3 4; 3 4 5];
I want a mean output matrix "c," whose output should be
c= [1.5 2.5 3.5; 2.5 3.5 4.5].
so basically "c" should have a mean of respective parameters and same dimension as "a" and "b". Can someone help?
Thanks, Subrat
  1 Kommentar
Yanbo
Yanbo am 15 Aug. 2012
you might just simply add a to b, and them divide the sum by 2. Or, are you looking for a specific command?

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Akzeptierte Antwort

Oleg Komarov
Oleg Komarov am 15 Aug. 2012
Unfortunately your example doesn't allow to propose a unique solution, i.e.:
c1 = [mean(a); mean(b)]
c2 = squeeze(mean(cat(3,a,b),3));
c1 simply takes the vertical mean (along rows) of a and then concatenates the vertical mean of b
c2 takes the mean of row 1 from a AND b and then concatenates the mean of the second row fro the two matrices.
Which one do you want?
  2 Kommentare
Subrat kumar sahoo
Subrat kumar sahoo am 15 Aug. 2012
Thanks Oleg, I wanted the operation like c2 is what I was looking for. Thanks again. Subrat
Subrat kumar sahoo
Subrat kumar sahoo am 15 Aug. 2012
I have a bit different requirement now: if "a" and "b" happens to be two elements of the same cell like d{1} and d{2} then is there a possibility of getting "c2" (*c2 = squeeze(mean(cat(3,a,b),3));*) with elements "a" and "b" (i.e. now d{1} and d{2}) picked thru a "for" loop? Thanks, Subrat

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Weitere Antworten (3)

Image Analyst
Image Analyst am 15 Aug. 2012
a = [1 2 3; 2 3 4];
b = [2 3 4; 3 4 5];
c = (a+b)/2
In the command window:
c =
1.5 2.5 3.5
2.5 3.5 4.5
  3 Kommentare
Alfredo Scigliani
Alfredo Scigliani am 25 Apr. 2023
what if you have a ridculous amount of matrices (1000) and you want to find the average? I think a for loop, but not sure how.
Steven Lord
Steven Lord am 25 Apr. 2023
what if you have a ridculous amount of matrices (1000)
Then I'd recommend you revise the code to avoid that scenario. More likely than not you dynamically created variables with numbered names like x1, x2, x3, etc.
Can you do that? Yes.
Should you do this? The general consensus is no. That Answers post explains why this is generally discouraged and offers several alternative approaches.

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Thomas
Thomas am 15 Aug. 2012
Bearbeitet: Thomas am 15 Aug. 2012
a = [1 2 3; 2 3 4];
b = [2 3 4; 3 4 5];
c=[mean(a);mean(b)]

Benjamin Klugah-Brown
Benjamin Klugah-Brown am 9 Aug. 2020
what if matrix a and b have different size
  5 Kommentare
Benjamin Klugah-Brown
Benjamin Klugah-Brown am 10 Aug. 2020
Thanks very much... by the ways does it work for NA too?
Walter Roberson
Walter Roberson am 10 Aug. 2020
If by NA you mean NaN, then you would have to use
mean(cat(3, A1, B1), 3, 'omitnan')
or you would have to use something like
maskA = isnan(A1);
maskB = isnan(B1);
C1 = (A1 + B1) / 2;
C1(maskA) = B1(maskA);
C1(maskB) = A1(maskB);

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