Matlab：从ODE45导出变量

Question

I have an ODE that uses many functions. I wish to export these "helper" functions so that I may graph them vs the independent variable of the ODE.

function dFfuncvecdW = ODE(W,Ffuncvec); 
X = Ffuncvec(1); 
y = Ffuncvec(2); 

#lots of code
R = ... #R is a function of X,W and y.
#and a few other functions that are a function of X,W and y.

dXdW = ... #some formula
dydW = ... #some formula
dFfuncvecdW = [dXdW; dydW];

end

I call this function with:

Wspan = [0 8000.]
X0 = [0; 1.]
[W,X] = ode45(@ODE, Wspan, X0);

I can easily output X or W to an excel file:

xlswrite(filename,X,'Conversion','A1');

But I what I need is to save "R" and many other functions' values to an Excel file.

How do I do that?
I am still extremely new to Matlab. I usually use Polymath, but for this system of ODE's, Polymath cannot compute the answer within a reasonable amount of time.

EDIT1: The code I use was generated by Polymath. I used a basic version of my problem so that Polymath may excecute the program as it only gives the Matlab code once the Polymath code has succefully run. After the export, the complete set of equations were entered.

Answer 1

The easiest, and possibly fastest, way to handle this is to re-evaluate your functions after ode45 returns W and X . If the functions are vectorized it will be easy. Otherwise, just use a simple for loop that iterates from 1 to length(W) .

Alternatively, you can use an output function to save your values on each iteration to a file, or a global , or, most efficiently, a sub-function (aka nested function ) variable that shares scope with an outer function (see here , for example). See this answer of mine for an example of how to use an output function.

Answer 2

I found a rather quick and painless solution to my answer. I merely appended a text file with code inside the ode function.

EDIT: I am unable to comment because I do have enough rep on this branch of SE. My solution was add the following code:

fid = fopen('abc1.txt', 'at');
fprintf(fid, '%f\n', T);
fclose(fid);

right above

dYfuncvecdW = [dFAdW; dFBdW; dFCdW; dFDdW; dydW]; 

at the end of the ode function. This proved to be a temporary solution. I have opened another question about the output I recieved.