How can I create variables from a matrix (4 x m), so that every column is a variable ? In the code I have 2 elements (N=2), but I need to do it also with 6, 8 10 elements.

N=2; % elements
L=1/N;
L=zeros(1,N)+L;
y=0:L:1;
Nf=NaN;
syms x NaN
for i=1:length(y)
    if i-1==0
        fa(i)=NaN;
    elseif i-1==1
        fa(i)=NaN;
    else fa(i)=0;
    end
    if i-1==0
        fb(i)=NaN;
    else
        fb(i)=(x-y(i-1))/L(i-1);
    end
    if i+1>N+1
        fc(i)=NaN;
    else
        fc(i)=(y(i+1)-x)/L(i);
    end
    if i+1>=N+1
        fd(i)=Nf;
    else
        fd(i)=0;
    end
end
f=[fa; fb; fc; fd]

[dpb]

Don't even THINK about wanting to do this -- it only leads to obuscated code when then try to subsequently do something with those variables.

Use the array indices instead or, at worst, create a struct or a table that contains the variable names such that fields or table variables can be created/referenced programmatically.

[DGM]

This is relevant.

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Long story short: arrays are indexable programmatically. Variable names are not programmatically indexable without opening up a can of worms that you should want to avoid unless you actually like causing problems for yourself.

As dpb mentioned, there are options like structs or tables that might be more desirable for the way they allow you to describe and organize their contents.

[Ravi Narasimhan]

To pile on: I use tables a lot but also Map Containers for associating keys with values when appropriate.

e.g.

A = magic(4)

A = 4×4

16 2 3 13 5 11 10 8 9 7 6 12 4 14 15 1

keySet = [1,2,3,4]; % Can be almost anything including chars if desired
valueSet = {A(:,1), A(:,2), A(:,3), A(:,4)}; % Associate a value with each key
B = containers.Map(keySet, valueSet)

B = 
  Map with properties:

        Count: 4
      KeyType: double
    ValueType: any

B(3) 

ans = 4×1

3 10 6 15

B(22) = [1 0 1 0] % Add to it. The 22 is a key vs. an array element

B = 
  Map with properties:

        Count: 5
      KeyType: double
    ValueType: any

keys(B)

ans = 1×5 cell array
    {[1]}    {[2]}    {[3]}    {[4]}    {[22]}

values(B)

ans = 1×5 cell array
    {4×1 double}    {4×1 double}    {4×1 double}    {4×1 double}    {[1 0 1 0]}

Further details are available at https://www.mathworks.com/help/matlab/map-containers.html