Have class vector; how obtain vector of a field?

Hello,

I have a vector (1D array) of a class that has several fields.

When working with my class, I would like to sometimes obtain a simple vector of a specific field, but I have only been able to do that with a for loop. There must be a better way!

For example, I have a class to represent a person called meep. A field within meep is age.

If I have vector containing 1000 meep, I might like to extract a numeric vector containing just the ages.

I thought something like

ages=meep(:).age; 

might do the trick, but it just gives the age of the last element of the meep vector. I've resorted to this static helper function within my class:

function param=paramVec( mVec, field )
                n=length(mVec);  %number of meeps; object mVec is expected to be a vector
                param=-99*ones(n,1); %one spot per meep
                for i=1:n   %go through meep vector
                	param(i)=mVec(i).(field);
                end
end   %end of return vector of requested parameters static function

Can someone suggest a more sensible and faster running approach?

Thank you, David

Answer 1

[Guillaume]

ages = [meep.age];  %same as: ages = horzcat(meep.age);
%or
ages = vertcat(meep.age);  %to vertically concatenate all the values

See the documentation on comma separated lists for details of how this work.

If for some reason, the fields/properties cannot be concatenated (because they don't have a common size in at least one dimension), then:

ages = {meep.age};  %to store them as a cell array

[David W Purcell]

Thank you for your help. That is much better!!!!