conversion frm sym to double is not possible?

clc;
clear all;
g_db=[0:1:40];

g=10.^(g_db/10);
c=1;
syms y
%g=0:0.1:10;
alpha=1;
p=0.5*((g)+exp(-g.*y));
q=((y.^(alpha-1)).*exp(-y./c))/((gamma(alpha))*(c^alpha));
r=p*q;
semilogy(g_db,r,'o')
hold on

[khushi]

but again error is coming undefined linespace argument for double..plz help

[Walter Roberson]

linspace not linespace

Answer 1

[Walter Roberson]

Your y is a symbol. p uses y so p is symbolic. q uses y so q is symbolic. Two symbolic values multiplied together is going to be symbolic. Therefore r is symbolic.

You then try to semilogy() with the second argument being that symbolic r. semilogy is not able to plot symbolic results.

In order to plot something that is in symbolic form, all of the symbolic variables in the expression must be given specific numeric values. For example,

semilogy(g_db, double(subs(r,y,linspace(0,1,20)), 'o')