How to select array elements which are within a range and get their indices?

Hi, I would like to get the value and index of elements from a cell array. For instant, I wanted to get the values and indices of the elements which falls within the range 0.95< x <1.15 from the row 'data{1,1}(:,5)'. Then I need to calculate the average of these elements.

I have thousands of elements in a row and I need to repeat the process for hundreds times. How do I do it efficiently?

Thank you in adv.

[the cyclist]

Note that your statement

0.95 < x < 0.15

would exclude all x. It looks like Image Analyst and I interpreted what you meant in different ways, so be careful about how you implement our code (if you do).

[Jo 5]

Sorry typo! Should be 0.95 < x < 1.15. Appreciate your help!

Answer 1

[Image Analyst]

Try this:

% Get the whole row
row = data(...........whatever...
% Find values of row in the range  "0.95< x <0.15"
% where x is either below 0.15 OR more than 0.95 but not in between.
logicalIndexes = row < 0.15 | row > 0.95;
% Get means where row is in range
meanValue = mean(row(logicalIndexes));
% You don't need the actual index numbers but if you want them, you can get them with find():
linearIndexes = find(logicalIndexes);

[Jo 5]

it works! Thank a lot :)

[Image Analyst]

With your typo fixed, you'd change from OR to AND:

logicalIndexes = (row > 0.95) & (row < 1.15);

Answer 2

[the cyclist]

I am not certain I understood exactly what you wanted, but this solution is probably close enough that you can figure it out:

% Make up some pretend data
rng default  
C{1} = rand(1,50);
C{2} = rand(1,100);

% For each element of the cell array, calculated the mean of the vector elements that lie strictly within the range (0.15,0.95)
meanWithinRange = cellfun(@(x)mean(x(x>0.15&x<0.95)),C)