## Avoid infinity in the answer

### Chanaka Navarathna (view profile)

on 9 Feb 2019
Latest activity Commented on by Chanaka Navarathna

on 11 Feb 2019

### John D'Errico (view profile)

Hi,
I am trying to run this code and, I always get infinity for my first iteration. Is there a way to avoid that? or at least filter that answers which gives infinity.
for i=1:M %for loop for M repetitions
Nx=N+randn(1,M)*CN; %excitation photon fluctuation
Nt=Nx*10.^-(E*C*l); %Nt = transmitted photons
SD2=sqrt(Nt); %This relationship is only valid for a Poisson distribution.
Nt1=Nt+randn(1,1)*SD2; %Nt = transmitted photon fluctuation
Nt2=mean(Nt1)+sqrt(Nt1)*randn(1,1); %detected photon fluctuation
A(i)=-log(Nt2/Nx); %calculation of absorbance
meanA=mean(A); %mean absorbance signal
standdeviationA=std(A); %noise
SNRUV(i)=meanA/standdeviationA %1/RSD=Signal to noise ratio for absorbance
end

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Star Strider

### Star Strider (view profile)

on 9 Feb 2019
What are the variable values (‘M’,‘CN’,‘E’), etc.?
Star Strider

### Star Strider (view profile)

on 9 Feb 2019
Reiterating:
What are the variable values (‘M’,‘CN’,‘E’), etc.?
Knowing the relevant function arguments is important. We could make wild guesses for them and never come close to the expected values for them.
Chanaka Navarathna

### Chanaka Navarathna (view profile)

on 9 Feb 2019
N,E,C,Q,f,l,CN,M = 1000000,10000,10*10^-6,0.6,0.01,1,1000, 10 respectively

### John D'Errico (view profile)

on 9 Feb 2019
Edited by John D'Errico

### John D'Errico (view profile)

on 9 Feb 2019

Sorry. I had a typo in what I entered before.
The first time through the loop. what do you expect?
A is a scalar on the first time throguh. What is the standard deviationm of a scalar variable? ZERO.
Then you divide by that standard deviation, so you get inf. Only you know what it is that you SHOULD do in that case.

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Chanaka Navarathna

### Chanaka Navarathna (view profile)

on 11 Feb 2019
Took the SNR calculation out from the loop and it was resolved. Thank you.