Whats wrong with this code?

N = 25;        
sigmaratio = 0.01;  
PD = zeros(1,1000); 
SNR = zeros(1,1000);

PF  = 0.00001; 
count = 0;
for sigmaratio=0.01:0.01:10
    count=count+1;
    TH = sqrt(sigmaratio/N) * chi2inv(PF); 
    SNR(count) = 10*log10(sigmaratio);  
    PD(count) = chi2cdf(PF)*(TH/(sigmaratio+1));  
end
figure;
plot(SNR, PD, 'b-');  
xlabel('Signal to noise ratio(DB)');
ylabel('Probability of detection, PD');
hold on;

PF = PF*10; 
count = 0;
for sigmaratio=0.01:0.01:10
    count=count+1;
    TH = sqrt(sigmaratio/N) * chi2inv(PF);

      PD(count) = chi2cdf(PF)*(TH/(sigmaratio+1));
  end

plot(SNR, PD, 'b-');
hold on;

PF = PF*10;
count = 0;
for sigmaratio=0.01:0.01:10
    count=count+1;
    TH = sqrt(sigmaratio/N) * chi2inv(PF);

      PD(count) = chi2cdf(PF)*(TH/(sigmaratio+1));
  end
  plot(SNR, PD, 'b-');
  hold on;

PF = PF*10;
count = 0;
for sigmaratio=0.01:0.01:10
    count=count+1;
    TH = sqrt(sigmaratio/N) * chi2inv(PF);

      PD(count) = chi2cdf(PF)*(TH/(sigmaratio+1));
  end
  plot(SNR, PD, 'b-');
  hold on;

PF = PF*10;
count = 0;
for sigmaratio=0.01:0.01:10
    count=count+1;
    TH = sqrt(sigmaratio/N) * chi2inv(PF);

      PD(count) = chi2cdf(PF)*(TH/(sigmaratio+1));
  end
  plot(SNR, PD, 'b-');
  hold on;

[Stephen23]

"Whats wrong with this code?"

No comments, no explanation, no introduction, no help, no examples, no idea what it should do...

Answer 1

[dpb]

Trying to run it, I get--

...
Error using chi2inv (line 22)
Requires two input arguments. 
>>

Don't know what the intent is and with, as you note Stephen, no explanations, I'm not going to try to divine but need a DOF argument as the second argument to chi2inv

Whether that should be N or perhaps count OP will have to determine...

[dpb]

Moved OP's "Answer" followup here--dpb

I need to obtain this graph. Can you guide me through the coding?

[dpb]

Well, what else do you need besides that which I've already pointed out? I have no way of knowing the response function; what "Energy Detector" in particular???