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

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Bathala Teja
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)
  2 Comments
Bathala Teja
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.....

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Answers (2)

Abolfazl Chaman Motlagh
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
  2 Comments

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Walter Roberson
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 = 
  2 Comments
Walter Roberson
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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