How to define an array based on Simulink simulation time?

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guo qing
guo qing 2024-6-5
评论： guo qing 2024-6-5
Hello everyone, I'm attempting to define an array in a MATLAB Function block based on the simulation time in Simulink. In my code, I use 'times index' to record the number of simulation steps. I have set the time step to 0.01s.To achieve this goal, I used 'persistent' variables, but encountered an error. How can I implement my objective?
function [y,y1] = fcn(u)
persistent inputs; % 声明一个持久变量用于保存输入值
persistent time_index;
if isempty(inputs) % 如果持久变量为空，则初始化
inputs = u; % 将当前输入值保存到持久变量中
time_index = 1;
else
inputs = [inputs, u]; % 将当前输入值追加到持久变量中
time_index = time_index + 1;
end
% 计算平均值
mean_val = mean(inputs);
% 计算差值的平方
diff_squared = (inputs - mean_val).^2;
% 计算方差
y = sum(diff_squared) / length(inputs);
all_inputs(time_index) = u;
y1=all_inputs;
This is the error I encountered.

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回答（1 个）

Rishav
Rishav 2024-6-5
Hi guo,
I understand that you are trying to initialize an array based on Simulink simulation time but encountering the 'Undefined function or variable "all_inputs"' error.
The issue here is that you are trying to use 'all_inputs' without declaring it as a 'persistent' variable, which would cause errors.
Just add the following line in your code:
persistent all_inputs;
  2 个评论
guo qing
guo qing 2024-6-5
Hello, thank you for your response. I wanted to ask why it is necessary to name it as a persistent variable. Are there any other ways to initialize an array based on time in Simulink?"
guo qing
guo qing 2024-6-5
I tried the operation you suggested, but MATLAB requires me to initialize all_inputs using the if isempty command and it cannot be an empty array. Clearly, the size of the all_inputs array will change over time, for example, with changes in simulation time. Is there a good way to solve this problem, or do I have to

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