input variable in evalin

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kman
kman 2017-10-31
评论： Walter Roberson 2017-10-31
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.

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Birdman
Birdman 2017-10-31
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)))
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Birdman
Birdman 2017-10-31
Hi Stephen,
I did not recommend him to use eval function. Thank you for your attention once more.
Walter Roberson
Walter Roberson 2017-10-31
There are some symbolic tasks that still need evalin(symengine) or feval(symengine), but those are somewhat advanced tasks.

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