[nemo]

syms r,E;

E=(4*r^2)/(3*exp((4*r^2)/5));

>> r=linspace(0,105*10^-9,30);
>> plot(r,Ez)
??? Error using ==> plot
Conversion to double from sym is not possible.

>> subs(Ez,r);
>> plot(r,Ez)
??? Error using ==> plot
Conversion to double from sym is not possible.

怎么出来图呢？用ezplot也不行，就成了一条直线。
我前面的r因为要求微分 积分，所以没改成数值。