# How to form a function using 'for loop' without 'sym' command

2 views (last 30 days)
Bathala Teja on 6 Sep 2021
Commented: Walter Roberson on 7 Sep 2021
i tried like this
m = 150;
Aos = 40;
nAi = 0;
for i=1:2:m
nAi = @(phi)nAi+cos(i*phi);
end
nA = vpa((nAi+Aos), 4)
Iam getting this error
Operator '+' is not supported for operands of type 'function_handle'.
Error in ll (line 8)
nA = vpa(nAi+Aos, 4)
Jan on 6 Sep 2021
You did not mention, what you try to achieve. All we see is the failing code. This is not enough information to guess, what you want to get instead.
Bathala Teja on 7 Sep 2021
Its clearly there. i want to form nA interms of phi.
But i want to evalute without sym. Any idea.....

Abolfazl Chaman Motlagh on 6 Sep 2021
Assuming you want nA be function of phi, you can use symsum for summuation :
m = 150;
Aos = 40;
syms phi k
nAi =@(phi) symsum(cos(2*k*phi),k,1,m/2);
nA =@(phi) vpa((nAi(phi)+Aos), 4);
% example
nA(pi)
ans =
115.0
Walter Roberson on 6 Sep 2021
syms is an abbreviation for sym() so this does not satisfy the requirement to not use sym
Abolfazl Chaman Motlagh on 6 Sep 2021
Oh! sorry, i just read the content not title of question.

Walter Roberson on 6 Sep 2021
m = 150;
Aos = 40;
nAi = @(phi) zeros(size(phi));
for i=1:2:m
nAi = @(phi)nAi(phi)+cos(i*phi);
end
nA = @(phi) nAi(phi)+Aos
nA = function_handle with value:
@(phi)nAi(phi)+Aos
You asked to avoid sym, so it seems likely to me you want to avoid using vpa() as well. But if using a final vpa is okay, then
vpa(nA, 4)
ans =
Bathala Teja on 7 Sep 2021
Edited: Bathala Teja on 7 Sep 2021
How to show result like this(ans which you shared) without vpa??
And you got result in the form of phi(means symbol), how to get symbol in place of phi??
Walter Roberson on 7 Sep 2021
With vpa(), the symbol for phi appears if you are using LiveScript, but not for traditional .m files.
To get the result without using vpa:
m = 150;
Aos = 40;
nA = str2func("@(phi) " + strjoin(compose("cos(%d*theta)", 1:2:m), " + ") + " + " + string(Aos))
nA = function_handle with value:
@(phi)cos(1*theta)+cos(3*theta)+cos(5*theta)+cos(7*theta)+cos(9*theta)+cos(11*theta)+cos(13*theta)+cos(15*theta)+cos(17*theta)+cos(19*theta)+cos(21*theta)+cos(23*theta)+cos(25*theta)+cos(27*theta)+cos(29*theta)+cos(31*theta)+cos(33*theta)+cos(35*theta)+cos(37*theta)+cos(39*theta)+cos(41*theta)+cos(43*theta)+cos(45*theta)+cos(47*theta)+cos(49*theta)+cos(51*theta)+cos(53*theta)+cos(55*theta)+cos(57*theta)+cos(59*theta)+cos(61*theta)+cos(63*theta)+cos(65*theta)+cos(67*theta)+cos(69*theta)+cos(71*theta)+cos(73*theta)+cos(75*theta)+cos(77*theta)+cos(79*theta)+cos(81*theta)+cos(83*theta)+cos(85*theta)+cos(87*theta)+cos(89*theta)+cos(91*theta)+cos(93*theta)+cos(95*theta)+cos(97*theta)+cos(99*theta)+cos(101*theta)+cos(103*theta)+cos(105*theta)+cos(107*theta)+cos(109*theta)+cos(111*theta)+cos(113*theta)+cos(115*theta)+cos(117*theta)+cos(119*theta)+cos(121*theta)+cos(123*theta)+cos(125*theta)+cos(127*theta)+cos(129*theta)+cos(131*theta)+cos(133*theta)+cos(135*theta)+cos(137*theta)+cos(139*theta)+cos(141*theta)+cos(143*theta)+cos(145*theta)+cos(147*theta)+cos(149*theta)+40

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