Try it this way:
% Demo by Image Analyst.
clc; % Clear the command window.
fprintf('Beginning to run %s.m ...\n', mfilename);
s = struct( ...
'name', {'mary','john','anna','paul','elaina'}, ...
'gender',{'f', 'm', 'f', 'm', 'f'}, ...
'age' ,{25, 35, 30, 22, 38} );
filterpatients_struct(s)
fprintf('Done running %s.m\n', mfilename);
function patientNames = filterpatients_struct(data)
allNames = {data.name}
allGenders = {data.gender}
allAges = [data.age]
% Get indexes of females:
femaleIndexes = contains(allGenders, 'f')
% Get indexes where age is between 30 and 40 inclusive:
ageIndexes = (allAges >= 30) & (allAges <= 40)
% Get names where both criteria are true:
bothTrue = ageIndexes & femaleIndexes
patientNames = allNames(bothTrue)
end