How do I solve Check for incorrect argument data type or missing argument in call to function 'exp' MATLAB

M=4;
a= log2(M);
g = (sin(pi/M))^2;
SNRdB=0:2:10;
for ii=1:size(SNRdB,2); 
    EbNodB = SNRdB(ii);   
end

for jj=1:length(SNRdB) 
    SNR(jj)=10^(EbNodB./10);
end  
z = SNR(ii);     
sym fi
fx=exp((1+(g.*z.*a./((sin(fi))^2))));
y=int(fx,0,((M-1)*pi)/M);

[Reyhan]

The error is; Check for incorrect argument data type or missing argument in call to function 'exp'.

Answer 1

[Steven Lord]

The command

sym fi

ans = 

fi

does not create a symbolic variable named fi in the workspace. You can see this by asking what variables are in the workspace:

whos

  Name        Size            Bytes  Class    Attributes

  ans         1x1                 8  sym                
  cmdout      1x33               66  char               

So when you use fi on the next line it calls the fi function with 0 inputs and attempts to call exp on that fixed-point variable.

x = fi

x = 

[]

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 16
        FractionLength: 15

The exp function is not defined for fi objects.

which -all exp(x)

'exp(x)' not found.

Compare to a sym object, which does have an exp method defined.

z = sym('z');
which -all exp(z)

/MATLAB/toolbox/symbolic/symbolic/@sym/exp.m  % sym method

So exp(z) will work (and call the sym method) while exp(x) will not (it will call neither the sym method nor the built-in function.)

y1 = exp(z)

y1 = 

y2 = exp(x)

Check for incorrect argument data type or missing argument in call to function 'exp'.

When you call sym in your function to define fi, I recommend always calling it in function form with an output argument like I did to define z.

fi = sym('fi');