Multiple selection of an array

Hello everyone,

i have an array of 150.000 rows, and i want to take the means of 300 rows once every 1460 rows. for example mean of row 1100:1400 and mean of row 2560:2860.

M = mean([

flow(1100:1400);

flow(2560:2860);

flow(4020:4320); ])

i have to take 100 means, but i only get 1 output when i use this. flow is the name of the array i use.

Answer 1

[fred ssemwogerere]

Hello, based on the indexing used in your question, i think something like this could do:

% Assuming your matrix or vector to be: "t", having 150,000 rows
t;
% Assume the starting index for averaging 300 rows at a defined interval to be; "i"
i=1100;
% Set interval over which to average every 300 rows
interval=1460; % interval over which the start of the next 300 rows will be chosen
% Number of rows from your matrix or vector; "t"
nrows=length(t);
% Using a "for" loop
for k=1:ceil(nrows/interval) 
    if i+300<=nrows % this condition prevents averaging beyond the length of the array
        avg_flow(k,1)=mean(t(i:i+300,:)); 
    else
    end
        i=i+interval;
end
% Please note the length of "avg_flow" will determine the total number of intervals taken for a given starting index.

Answer 2

[Star Strider]

Using a simple loop:

Array = rand(150000,1);                                 % Create Array

v = [1100 : 1460 : numel(Array)];
for k = 1:numel(v)
    ArrayMean(k) = mean(Array((0:299)+v(k)));
end

Answer 3

[Matt J]

You can use sepblockfun downloadable from here

https://www.mathworks.com/matlabcentral/fileexchange/48089-separable-block-wise-operations

as follows

M=sepblockfun(flow,[300,inf])