Accessing values of fieldnames in a structure without using the fieldnames function

Hi all,

I've got a structure which has 20 different field names, e.g. 'fieldname01','fieldname02' etc.

Each fieldname has a numeric value, such as:

fieldname01: 0.56 fieldname02: 0.93 fieldname03: -0.34

Up to fieldname20

I need to access the numeric values of certain field names, for example the 2nd, 5th and 15th. Just wondering what would be the right way about doing this without using the fieldnames function if that's possible at all?

Thank you.

Answer 1

[Sven]

Hi Jess,

Use parentheses:

S = struct('field1',1,'field2',2)
fieldStr = ['fields' num2str(1)]
S.(fieldStr)
ans = 
   1

Or, with your particular example:

for i = 1:20
  val = S.(sprintf('fieldname%02d',i))
end

Please note however that the "right" way to store data from 1 to 20 isn't in a structure with the number built into the name. Instead it sounds like you should be using an array (or cell array if your datatypes are different).

For example:

myData = [12 10 3];

is much cleaner than:

myData.element1 = 12
myData.element2 = 10
myData.element3 = 3

[Jess]

Thank you so much!

[Jan]

+1 for mentioning, that an enumeration of fieldnames is much worse than using arrays.