How to call sequential variables with for loop matlab? [closed]

Answer 1

Use eval inside your loop:

eval(['I = length_act_', num2str(i)]);

Pro tip:
The eval command is usually slow and inefficient, use arrays instead. In your case, it seems that each of your "length_act_i" variables is a vector on its own, so you should be employing a cell array. For instance, call it length_act and set it like so:

length_act = {length_act_1, length_act_2, length_act_3, ...};

and then access each cell in the array using:

for i = 1:length(length_act)
    I = length_act{i};

    ...
end

Also, it is recommended not to use "i" and "j" as names for variables.