Assign a variable from within a function to the script I used to call the function from.

Hi,

I have ran in to a problem and I have been trying to deal with this for hours and I just don't get it... Help will be extremely appreciated!

The function looks like:

function [A,x] = fd4(L,N)

x = linspace(0,L,N+1)';

x(1) = []; % Remove first point

h = x(2)-x(1);

e = ones(N,1);

A = spdiags([e -4*e 6*e -4*e e], -2:2, N, N);

A(1,1:4) = [16 -9 8/3 -1/4];

A(end-1,end-3:end) = [16/17 -60/17 72/17 -28/17];

A(end,end-3:end) = [-12/17 96/17 -156/17 72/17];

B =0;

A = full(A);

A = A/h^4;

B = cond(A,inf)

assignin(UU2,'D',B)

Basically I have a matrix and through my other script I give the value input for L and N. My issues lies in the very end of the function. After I assign values for L and N, I calculate the cond(A, inv) and assigns this value to the variable B. I would like to transfer this value of B to another variable D (not used before) to the script I used to call the function from. I thought this could be done by assignin(UU2,'D',B) (UU2) is the name of my script where I call the function from. But I keep getting error messages that Im trying to run a script as a function:( help?

Best regards, Christoffer

Answer 1

[Jan]

Please read the documentation of assignin. There you find the explanation, that the 1st input is either 'base' or 'caller'. But you use a function call to the script, which starts this script for an evaluation. The appearing error message should be clear.

Better define an output argument:

function [A, x, B] = fd4(L, N)
...

Then call this function from your script like this:

[A, x, B] = fd4(L, N);

Then B is assigned as wanted without brute tricks as assignin, which impedes debugging due to magic remote creation of variables. A reader of your script cannot guess, where B comes from, when reading the code.

[Christoffer Thornvall]

Thank you so much! I tried to read several articles about assignin but I did not understand them, nor the error messaged I received. But thank you again