Initializing Array of Structures/Objects

I simply want to set each struct in a struct-array. I set structarray to [] as it is an object property in my case, where it is being initialized as emtpy array. My first approach looks like:

structarray = [];  
for i=1:10
    structarray(i) = struct('index', i);
end

I get the following error: 'The following error occurred converting from struct to double: Error using double Conversion to double from struct is not possible.'

I can use an if else check and set the first element by:

structarray = struct('index', i);

On http://www.ece.northwestern.edu/CFS/local-apps/matlabhelp/base/relnotes/matlab/matlab1212.html it reports that setting structarray(1) throws this error.

Is there any easy way to write this straightforward similar to my code above?

Answer 1

[Geoff Hayes]

Sven - why not use arrayfun to apply a function to each element in the array. In this case, your function would create a struct with a single field called index where its value is assigned its position/index within the array. The following should do what you require

 myStructArray = arrayfun(@(x)struct('index',x),1:10)

Note how the first input to arrayfun is the function that creates the struct given an input parameter. The value of each parameter is determined from the second input to arrayfun - an array of indices from one to ten.

Try the above and see what happens!

[mary]

How this can be done if there are for instance two fields?

Something like:

myStructArray = arrayfun(@(x)struct('index1',x),zeros(1,10))
myStructArray = arrayfun(@(x)struct('index2',x),zeros(1,10))

will replace the first field by the second one. The idea is to keep both index1 and index2.

[Bruno Luong]

@mary

myStructArray = arrayfun(@(i1,i2)struct('index1',i1,'index2',i2),zeros(1,10),zeros(1,10))

myStructArray = 1×10 struct array with fields:
    index1
    index2

[mary]

I found the answer:

myStructArray = arrayfun( @(x)struct('index1',x,'index2',x),zeros(1,10) )

Answer 2

[Walter Roberson]

structarray = struct('index', repmat({[]}, 1, 10));