error in finding the mean

I have found values of R and P

R(k) = n/8

P(k)= n/28

i have used this inside for loop ,the value of n varies,,i get 80 values for R and P ,each having 80 values,i want to find mean of every eight values of R and P tried

R1(x)=mean(R(:));

P1(x)=mean(P(:));

but getting same values for one value is repeated 10 times,

please help

[Chandra Kurniawan]

I think it's better if we can solve your multiple problem in this page.

http://www.mathworks.com/matlabcentral/answers/24932-selecting-the-images

and

http://www.mathworks.com/matlabcentral/answers/24976-replacing-the-parameters

[Chandra Kurniawan]

Just tell me what is 'n'?

[Pat]

n varies according to number of retrieved images for a query image,it is not constant

[Chandra Kurniawan]

Then, How can I get the value of n?

[Pat]

T=500;

c = find(R < T);

n=numel(c);

R =euclidean distance(80 values),i am finding values which are less than 500