在不知道尺寸的情况下在Matlab中预先分配空间？

Question

我正在Matlab中构建一个向量X，它通过在循环过程中连接每个迭代的结果。

我现在正在做的是

X=[];
for j=1:N
    %do something that delivers a vector A
    %X=[X;A]
end

不可能预先确定A的大小。有没有什么方法可以预先分配空间？

Answer 1

可能的解决方案：

A=cell(1,N); %Pre-allocating A instead of X as a cell array
for k=1:N    %I changed the name of loop variable since `j` is reserved for imag numbers
  %Here I am generating a matrix of 5 columns and random number of rows. 
  %I kept number of columns to be constant (5) because you used X=[X;A] 
  %in the question which means number of columns will always be same
  A{k} =  rand(randi([1,10],1,1),5); %doing something that delivers a vector A   
end
X = vertcat(A{:});