matlab - changing values of a global variable via command window

Question

Suppose you had a global variable G in a function f, say. The output of f is dependent on G, and G is declared to be global within f.

I would like f to work as follows through the command window:

• set G to some value
• run f, giving some result dependent on G
• set a different value of G
• run f again, giving an answer dependent on the new G

However, this has the following problem: it would involve defining G first, then declaring it to be global when f is run, which results in a matlab warning I would also require that the global variable G is not a direct input for f.

Any help to work around this, or if my method is fundamentally flawed, an alternative would be greatly appreciated.

Answer 1

Yes you can do this. A simple example:

In the command window, enter global G and G=2.

Then make a simple function, e.g.:

function incG
global G
G=G*2;
disp(G)

Run incG from the command window and see what happens. You can also modify the value of G in the command window in between executing incG. You do have to be careful that G exists and has the correct value when you run incG.