I'm learning about structure iteration, and trying to output things in the loop
patient(1).name = 'John Doe';
patient(1).billing = 127.00;
patient(1).test = [79, 75, 73; 180, 178, 177.5; 220, 210, 205];
patient(2).name = 'Ann Lane';
patient(2).billing = 28.50;
patient(2).test = [68, 70, 68; 118, 118, 119; 172, 170, 169];
fields = fieldnames(patient)
%numel is number of elements
for i=1:numel(fields)
fields(i)
patient.(fields{i})
end
During this patient.(fields{i}), it gives 'New Name' and [] which are not part of my struct. Where are those values coming from?
The output is:
ans = 'name'
ans = John Doe
ans = Ann Lane
ans = New Name
ans = 'billing'
ans = 127
ans = 28.5000
ans = []
ans = 'test'
ans = 79.0000 75.0000 73.0000
180.0000 178.0000 177.5000
220.0000 210.0000 205.0000
ans = 68 70 68
118 118 119
172 170 169
ans = []
You must have previously assigned patient(3).name = 'New Name' and since your code only over-writes the first and second elements of patient, the third element remains untouched and is therefore appearing during your looping.
You can check this by using size or numel
numel(patient)
% 3
To prevent this, you can either initialize your struct to an empty struct prior to assignment
% Initialize it
patient = struct()
% Now populate
patient(1).name = 'whatever';
Or explicitly clear the variable clear patient to ensure that this doesn't happen.
clear patient
% Now populate it
patient(1).name = 'whatever';
Also, as a side-note, the reason that the other fields are [] is because if you add a new field to an existing struct array, then all struct entries in the array will receive [] as the value for the new field
clear patient
patient(2).name = 'New Name';
patient(1).name = 'Test';
% Add a new field only to patient(2)
patient(2).date = 'today';
% patient(1).date becomes []
patient(1).date
% []