Function does not calculate desired variable.

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Giuseppe on 20 May 2014
Commented: Friedrich on 21 May 2014
Hi I have the following function;
function [EV,N,t,S] = EVjc300293(EV,N,t,S)
% If a variable is set to zero calculate its value.
% 1. Choose which variable to process.
if EV==0
EV = log2((N^2)/t)-log2(S/100);
elseif N==0
N = sqrt((2^(EV+log2(S/100)))*t);
elseif t==0
t = (N^2)/(2^(EV+log2(S/100)));
elseif S==0
S = 100/(2^(EV-log2((N^2)/t)));
end
end
I want to make it so that if a variable is set to zero in the function its value is calculated. I wish to do this using the if elseif statements listed. However when I run it it always calculates EV and not any other variable?
Thanks.
Giuseppe on 20 May 2014
I call it like this;
[N] = EVjc300293(10,0,3,5)
Where here for example I am trying to find N?

Friedrich on 20 May 2014
N is your second output so you would need to call it like this:
>> [~,N] = EVjc300293(10,0,3,5)
Friedrich on 21 May 2014
The other variables arent't calculated. Since output and input variables have the same name they are copied to the output variables. Your function always return 4 variables and you need to know/figure out which output variables are relevant for you:
[a,b,c,d] = EVjc300293(10,0,3,5)
You will see that a is 10, b got calculated and c is 3 and d is 5.

Chandrasekhar on 20 May 2014
In the function that you have written EV, N ,t,s are in separate if -else if conditions and only on of them executes at a time.
in you case if EV==0 is getting satisfied and hence only EV is being calculated and the else if and else conditions are not getting executed.
one solution is to assign a default value for all the value at the beginning of the function.
Giuseppe on 20 May 2014
Could you further explain this idea please?