# How to get a single value of an array through a function inside a script?

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Zahid Saleem on 8 May 2019
Edited: Stephen Cobeldick on 9 May 2019
Hello,
I have two questions, how can we use a variable defined in a script to be used later inside a function in the same script?
2nd, I am having trouble in trying to get a single value of an array which is processed inside a function inside a script. The function should return the u'th value of the array gE by storing it in the Eg(function return) but I get an error of
Index exceeds matrix dimensions.
Error in Slab_002>Esrc (line 187)
Eg = gE(u);
How can we fix this? All answers are welcome.
script something something
a = something;
gE = zeros(1, something);
dt = something;
STEPS = something;
function Eg = Esrc(u)
a = dt*u; %% I want to use the a that is defined above in the code.
for i = 1:STEPS
gE(i) = exp(-((t-t0-a)/tau).^2);
end
Eg = gE(u);
end

Kevin Phung on 8 May 2019
function Eg = Esrc(u,a)
a = dt*u; %% I want to use the a that is defined above in the code.
for i = 1:STEPS
gE(i) = exp(-((t-t0-a)/tau).^2);
end
Eg = gE(u);
end

Stephen Cobeldick on 9 May 2019
This does not make much sense:
function Eg = Esrc(u,a)
a = dt*u;
...
end
You added the inut argument a, but totally ignore that input argument inside the function by reallocating that variable name. What is the point of that?
Zahid Saleem on 9 May 2019
Well, I am trying to simulate maxwells equations using FDTD(Finite Difference Time domain), ome side of equation is temporal whereas the other side is spatial. I am fairly new to MATLAB so this was one of the easiest(inefficient) way to manage those equations differentials.