Function does not calculate desired variable.

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Giuseppe 2014-5-20

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评论： Friedrich 2014-5-21

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.

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Friedrich 2014-5-20

How do you call it? Name some examples

Giuseppe 2014-5-20

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I call it like this;

[N] = EVjc300293(10,0,3,5)

Where here for example I am trying to find N?

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Answer 1

Friedrich 2014-5-20

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N is your second output so you would need to call it like this:

>> [~,N] = EVjc300293(10,0,3,5)

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Chandrasekhar 2014-5-21

In this answer only N is being calculated since the if EV==0 condition has failed.. what abt others??

Friedrich 2014-5-21

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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.

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Answer 2

Chandrasekhar 2014-5-20

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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.