Extracting data from handle objects

Question

Marc Laub 2022-11-29

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1866323-extracting-data-from-handle-objects

回答： Askic V 2022-11-29

采纳的回答： Askic V

在 MATLAB Online 中打开

Hey, I have following problem.

I have multiple handle class objects which all have a propertie which can either be a scalar or a vector/matrix.

I now need a way to extract the last values of those vactors/matrices from all objects, so that they form a vector again.

So for example:

obj(1).value1=[1,2,3];
obj(1).value2=[0,0,0;0.1,0.2,0.3;0.9,0.8,0.7];
obj(2).value1=[1,2,3,4,5];
obj(2).value2=[0,0,0,0,0;0.9,0.7,0.8,0.6,0.5;0.1,0.2,0.3,0.4,0.5];
...

I now need to extract the data like

value1_vector=[3,5];
value2_vector=[0,0.3,0.7;0,0.5,0.5];

At the same time, these vectors/matrices have no fixed length and I dont know the length at the start. So it would be better to save same as a cell? Would that make the extracting of the values above easier?

Maybe a change in the size is not preferable when in future the code might be tranfered to a mexfile, where a size change while runtime is inmpossible.

Many thanks in advance

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Marc Laub 2022-11-29

Did my best to trace back the most valuable answers, except if the answer was within a comment...

Rik 2022-11-29

The best strategy for storing your data depends on what you want to do next.

Do not reject a solution with a loop out of hand. Loops are fast and are easy for Matlab (or a human) to translate to C(++).

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Answer 1

Askic V 2022-11-29

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1866323-extracting-data-from-handle-objects#answer_1115193

在 MATLAB Online 中打开

I hope this helps a bit:

clear
clc
obj_arr = struct('value1',[], 'value2',[]);
rng(0)
% Initialize obj_array
for ii = 1:2
    % generate random number of elements 
    nr_el = randi([2 6], 1,1);
    obj_arr(ii).value1 = randi(10,1,nr_el);
    obj_arr(ii).value2 = randn(nr_el,nr_el);
end
% Determine the size of obj_arr
N = length(obj_arr);
% vectors to store values
value1_vec = zeros(1, N);
value2_vec = [];
for ii = 1:N
    value1_vec(ii) = obj_arr(ii).value1(end);
    [r2, c2] = size(obj_arr(ii).value2);
    for jj = 1:r2
        value2_vec = [value2_vec, obj_arr(ii).value2(jj,c2)];
    end
end
value1_vec
value1_vec = 1×2
     3     8
value2_vec
value2_vec = 1×11
   -0.7549    1.3703   -1.7115   -0.1022   -0.2414    0.3192    2.3505   -0.6156    0.7481   -0.1924    0.8886