Error in ==> sym.sym>sym.double at 936 ; I want plot

hello everyone ,

I want find a maximum of z but it get error like :

??? Error using ==> mupadmex
Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.

If the input expression contains a symbolic variable, use the VPA function instead.

Error in ==> sym.sym>sym.double at 936
            Xstr = mupadmex('symobj::double', S.s, 0);

here is my code

syms E Eg V  ;
z=[ ];
y=[ ];
x=[];

for Eg=0.5:0.05:1.3; 

    z=[]; 
    a = quad( '(E.^2) ./ (exp(E./0.516)-1)', Eg , 100);

    for V=0:0.05:Eg;

      c=3 .*(10.^8); % m/s
      h=4.1361e-015; % eV.s
      k=8.62E-5;
      Tc=300;

      Pin = 1.4458e+026 ;

      g = (E.^2) ./ (exp( (E - V) ./0.0258)-1) ;
      b = double(int(g,Eg,100));
      P = ( 2.*V./6.3682e-027 ) .* ( a - b ) /Pin;

      z=[z P];
      m=max(z);

    end

y = [y m];

end

Eg=0.5:0.05:1.3;
plot(Eg,y)
title('Eg=0.5~1.3');
xlabel('Eg');
ylabel('η[max]');

If set b=0 , it getting a correct result , so I think b is the problem.

y=[y m] cant saving any data .

thanks every one :)

Answer 1

[Andrei Bobrov]

try

Eg=0.5:0.05:1.3; 
V=arrayfun(@(x)0:.05:x-.05,Eg,'un',0);
Pin = 1.4458e+026 ;
a = arrayfun(@(x1)quad(@(x)x.^2./(exp(x/0.516)-1),x1,100),Eg);
y = zeros(numel(Eg),1);
for j1 = 1:numel(Eg)
    b = arrayfun(@(v)quad( @(x)x.^2./(exp((x - v)/0.0258)-1),Eg(j1),100),V{j1});
    y(j1) = max( 2.*V{j1}./6.3682e-027 .* ( a(j1) - b ) /Pin );
end

plot(Eg,y)
title('Eg=0.5~1.3');
xlabel('Eg');
ylabel('η[max]')

[Tai-i]

The result met my expectation , thanks you very much ! ^_^

But i want to know what wrong with my code ?

[Tai-i]

I cant understand

V=arrayfun(@(x)0:.05:x-.05,Eg,'un',0);

could u explain plz? thx!

[Andrei Bobrov]

in this case:

we create cell array 'V' with size [1xlength(Eg)], 'V' contents double arrays - vectors (eg for first cell of V: 0,.05,.1,.15.....Eg(1)-.05), please read http://www.mathworks.com/help/techdoc/ref/arrayfun.html

[Tai-i]

now i got 0.05=.05 thx ^^