formation of a function like in Mathematica

Mathematica's ComplexExpand is a non-trivial symbolic process so to get it right you would need to be working with the Symbolic Toolbox. At the moment I do not see an equivalent routine in the Symbolic Toolbox. In the programming language Maple that the Symbolic Toolbox has many similarities to, the routine would be named evalc(), but MATLAB'S evalc() has nothing to do with that.

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Kashif 2015-8-6

在 MATLAB Online 中打开

Thanks for the reply, in my problem etp and etn are known values and these are not variables,

        %  Actually In Mathematica
% With the following function
% F[n_] := ComplexExpand[Im[etp[n]/(et[n] - (x + y I))]]
% n1 = n/8;
% n2 = n + n/8;
% et(n1)=8.33663 + 6.8417*1i;
% etp(n1)=-4.67008 + 10.1188*1i;
% et(n2)=0.641945 - 0.526831*1i;
% etp(n2)=-1.00014 - 0.25351*1i;
% I am  getting like following values of F(n1) and F(n2)
% F[n1]=116.308/((8.33663 - x)^2 + (6.8417 - y)^2) - (
%  10.1188 x)/((8.33663 - x)^2 + (6.8417 - y)^2) - (
%  4.67008 y)/((8.33663 - x)^2 + (6.8417 - y)^2);
% And
%  F[n2]=-(0.689644/((0.641945 - x)^2 + (-0.526831 - y)^2)) + (
%  0.25351 x)/((0.641945 - x)^2 + (-0.526831 - y)^2) - (
%  1.00014 y)/((0.641945 - x)^2 + (-0.526831 - y)^2);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % I am looking for the same function in Matlab, which may give me like 
% same values of f(n1) and f(n2) in Matlab, But with following
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
syms  x y real
syms f(n)
f(n) = simplify(imag(etp(n))/((et(n)) - (x + y * 1i)));
gradient(f(n), [x, y])
% with your command i am not getting the same values as above

Walter Roberson 2015-8-6

You are not likely to get those any time soon. MATLAB has a limited interface subset to the Symbolic Toolbox ('MuPAD') which is more powerful.

I was assisting you under the assumption that you wanted to make something work. The primary barrier to making something work is the definition of et and etp as objects that need to recognize two specific inputs and return specific arbitrary outputs for those two inputs while being meaningfully defined symbolically for the formula with indefinite n.

Kashif 2015-8-8