How can I implement an array of function handles that takes a struct as input and calculates the function value for each function handle?

I have function handles, e.g. area_rectangle and area_circle, and structs that contain information like input_variables.height = 3.

function area_rectangle = area_rectangle(input_variables, constants)

    if ~isfield(input_variables,'height') || ~isfield(input_variables,'width') 
        area_rectangle = NaN;
    else    
        area_rectangle = input_variables.width * input_variables.height;
    end

function area_circle = area_circle(input_variables, constants)

      if ~isfield(input_variables,'radius') || ~isfield(constants,'pi') 
          area_circle = NaN;
      else    
          area_circle = constants.pi * input_variables.radius^2;
      end

Unfortunately, cell arrays can't be used because they need some kind of index support:

     >> test = cell(2,1)

        test = 

            []
            []

      >> test{1}=@area_rectangle;
      >> test{2}=@area_circle;
      >> test

      test = 
          @area_rectangle
          @area_circle
      >> input_variables = struct('height',3,'width',2,'radius',1)

    input_variables = 

        height: 3
         width: 2
        radius: 1
  >> constants = struct('pi',3.14159)

constants = 

      pi: 3.1416
  >> test(input_variables,constants)
    Error using subsindex
    Function 'subsindex' is not defined for values of class 'struct'

How can I use function handles and structs at the same time?

Thanks in advance.

Answer 1

[Jan Orwat]

Hello Carolin, you can evaluate functions in a loop:

>> values = zeros(1,length(test));
>> for k = 1:length(test)
       values(k) = test{k}(input_variables,constants);
   end
>> values

values =

    6.0000    3.1416

or using cellfun():

>> values = cellfun(@(F)F(input_variables,constants),test)
values =

    6.0000    3.1416

cellfun looks more compact, but it is often harder to read and modify, especially when you are going back to the piece of code after a while.

[Carolin Katzschke]

Hi Jan,

thank you very much for your quick answer. Both possibilities are correct solutions, but for my upcoming work I prefer the second.

Thanks, Carolin