assigning a a structured 2x2 matrix using a loop

Question

rony 2013-4-13

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/71877-assigning-a-a-structured-2x2-matrix-using-a-loop

I have written code like this:

detresp = struct ('a','b','c','d');

and later in the code comes a while loop where i have to use an array of detresp structures.

centroid is a precomputed M*2 matrix. I need to assign centroid to 'a' field of each cell of the detresp array.

the line: detresp(framecount).a=centroid;

throws an error saying that the left hand side is not a valid target for assignment. Any help is highly appreciated.

Thank you.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

ChristianW 2013-4-13

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/71877-assigning-a-a-structured-2x2-matrix-using-a-loop#answer_82095

在 MATLAB Online 中打开

M = 5;
centroid = rand(M,2);
detresp = struct('a',num2cell(centroid,2),'c','d');

or

detresp = struct('a',cell(M,1),'c','d');
for k = 1:M
    detresp(k).a = centroid(k,:);
end

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 2

Image Analyst 2013-4-13

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/71877-assigning-a-a-structured-2x2-matrix-using-a-loop#answer_82096

在 MATLAB Online 中打开

It's a bit tricky and unexpected. You need to preallocate all the members that you will ever need. See this example:

numberOfFrames = 5; % Whatever...
% Preallocate all the a, b, c, and d that we will ever need.
a = zeros(numberOfFrames, 2);
b = zeros(numberOfFrames, 1);
c = zeros(numberOfFrames, 1);
d = zeros(numberOfFrames, 1);
detresp = struct('a', 'b', 'c', 'd')
for k = 1 : numberOfFrames
  detresp(k).a = rand(2,1)
  detresp(k).b = rand(1,1)
  detresp(k).c = rand(1,1)
  detresp(k).d = rand(1,1)
end