Is there a efficient way to substitute variables into a symbolic array?

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Ben Ma 2015-1-30

1
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https://ww2.mathworks.cn/matlabcentral/answers/173603-is-there-a-efficient-way-to-substitute-variables-into-a-symbolic-array

评论： Ben Ma 2015-1-31

In the former version of MATLAB I can use subs to do this:

syms x;
subs([x/2 x^2],[x],[1]);
ans
class(ans)

And I'll get

ans=
0.5 1
ans=
double

Now when I use subs, class(ans) will be syms. It's easy to bypass it by using eval(subs()) instead of subs(). But when i try to run these code I found:

clear all
syms x y
a=[x y];
tic
for i=1:100
subs(a,[x y],[1 1]);
end
toc

I just get more than 1 sec in MATLAB 2014b and about 0.07 sec in MATLAB 2008a. With eval() it's even 0.03 sec slower. I'm working on a computation program, and time efficiency is very important to me. So if there's some way to bypass this annoying (though it can helps remain accuracy in multiply calls of subs) feature of subs?

I've tried matlabFunction, and found it's more slower... 100 calls will consume more than 3 sec. And my input are all vectors, which makes anonymous functions, inline functions and matlabFunction imporper to me.