Saving a variable in a .mat file

Hello everyone,

I have a .m file where a function runs and outputs a series of variables. Right now, I am saving one values out of the if loop in the said function as such:

function [par, ta, xa] = swingup(par)

    if strcmp(par.run_type, 'learn')
        ...
        ra = zeros(par.trials, 1);
        ...
        
        for ii = 1:par.trials        
            x = swingup_initial_state();
            
            for tt = 1:ceil(par.simtime/par.simstep)
               
                ...
                    
                r = observe_reward(a, sP, par);
                ...  
                
                % Keep track of cumulative reward
                reward = r;
                ra(ii) = ra(ii)+reward;
                

                % TODO: check termination condition
                if is_terminal(s,par) == 1 
                    break;
                end         
            end
        end
        
        save('swingup', 'ra');
        
        

In the end, I am interested in saving 'ra' while changing some of the values which 'ra' depends on. So for example changing some values in 'par'. So what I want to achieve is:

1. Run the code
2. Save 'ra' as a .m file
3. Change a variable
4. Run the code again
5. Save the new value of 'ra' in a column next to the already existing one

The goal is to have a .mat file with each column the results of ra for different values so that I can plot them. How exactly can I achieve this?

[Stephen23]

You can either:

• load, change, save, or
• https://www.mathworks.com/help/matlab/ref/matlab.io.matfile.html

[GCats]

What I don't understand is how to prevent the new values overwrite the old one when running the same script.

Answer 1

[Dinesh Yadav]

Hi,

Have a look at this existing answer for the same question(link). It will resolve your issue.