Average certain rows in 3D matrix

Hi I have a 3D matrix X(63x180x360), I need to average the following elements:

X(4,:,:),X(5,:,:),X(6,:,:),X(9,:,:),X(11,:,:),X(17,:,:),X(28,:,:),X(38,:,:),X(43,:,:),X(50,:,:),X(57,:,:);

It should give me back a 3D matrix, is there a simple way, or even a general way to average certain rows

[James Tursa]

If you are doing an average, how do you get back a 3D matrix? For your example, what is the dimension of the result you want?

[Nadine]

You're so right, I've been thinking about it too, the final dimension would be something like X(1,180,360)

Answer 1

[dpb]

Can you write an expression to select the desired rows? If so, simply

ix=[4:6 9 11...];  % whatever is the logic to select the desired rows
mn=mean(x(ix,:,:),1);

Trivial example...

>> x=randn(3,2,5);
>> ix=[1,3];
>> mn=mean(x(ix,:,:),1);
>> whos x mn
Name      Size             Bytes  Class     Attributes

mn        1x2x5               80  double              
x         3x2x5              240  double

>>

Answer 2

[James Tursa]

Is this what you want?

rows = [4 5 6 9 11 17 28 38 43 50 57];
Y = mean(X(rows,:,:),1);