input variable in evalin

    y=double(evalin(symengine, 'binomial(2634,1)*binomial(1360*125-2634, 125-1)/binomial(1360*125, 125)'))

The above gives sume number y. but instead of 1 I want variable x in the above equation.

     function y=f(x)
     y=double(evalin(symengine, 'binomial(2634,x)*binomial(1360*125-2634, 125-x)/binomial(1360*125, 125)'))
     end

Of course this gives an error. How can I make function using the input variable x? Thank you.

Answer 1

[Birdman]

x=sym('x');
y=evalin(symengine, 'binomial(2634,x)*binomial(1360*125-2634, 125-x)/binomial(1360*125, 125)','x');
y=double(vpa(subs(y,x,1)))

[kman]

Thank you!!

[Birdman]

If the answer is useful, then accept the answer so that other people having the same problem will know there is a working solution.

[Stephen23]

Note that using evalin or eval is not recommended for using with symbolic equations, no matter how much beginners think they are and recommend them to each other. The correct operations are described in the MATLAB documentation: double, subs, or vpa. Symbolic language is not quite the same as MATLAB language, and using eval or evalin is simply the wrong tool for the task.

Read this comment from Steven Lord:

https://www.mathworks.com/matlabcentral/answers/356479-substituting-and-evaluating-function#comment_497058

[Birdman]

Hi Stephen,

I did not recommend him to use eval function. Thank you for your attention once more.

[Walter Roberson]

There are some symbolic tasks that still need evalin(symengine) or feval(symengine), but those are somewhat advanced tasks.