How do I multiply two functions handles?

%%---------constants:
Gma_32 = 100
Gma = 210e-15
gamma_u = 500
gamma_c = 50
a = Gma_32/sqrt(2*gamma_u*Gma)
n = 4e10
c1 = -4
c2 = 2.05
c3 = 1
K = 10



%--------Function
% 
% X = @(k) -4*n - a^2*n*sqrt(n) + 4*c1*k.^4 + (2*a*sqrt(n)-16*K^2 + 4*a*c1*c3*sqrt(n) + 8*n*c1*c2)*k.^2
% Sq = @(k) sqrt((-X(k) + sqrt(X(k).^2 + Y^2 ))/2)
% f = @(k) -2*k.^2 - 2*n - a*sqrt(n) + Sq(k)
% f2 = @(k) -2*k.^2 - 2*n - a*sqrt(n) - Sq(k)

%------------------------------Fns:
b_i = @(k) -4*c1*k*K
b_r = @(k) 2*k.^2 +2*n + a*sqrt(n)

c_i = @(k) ( 4*n*c2* - 2*(2*n + a*sqrt(n))*c1 + 2*a*sqrt(n)*c3 )*K*k
c_r = @(k) -(1 + c1^2)*k.^4 - (2*n -4*(1 + c1^2)*K^2 + sqrt(n)*c3*c1 + 2*n*c1*c2 )*k.^2
 
D_r = @(k)  b_r(k).^2 - b_i(k).^2 -4*c_r(k)  
D_i = @(k)  2*b_i(k).*b_r(k) - 4*c_i  

f = @(k) -b_i(k) + sqrt( -D_r(k) + sqrt(D_i(k)^2 + D_r(k)^2))/4
 
%-------Grid:
k = -200:0.1:200
% %-------Plot
% 

plot(k,f(k))
%plot(k,f2(k))

theres an error on line with function f, how do i multiply two functoin handles. or suggest a bwtter way of plotting this function.

[Steven Lord]

FYI for the future, when you're asking for help with code that throws an error message or issues a warning message please include the full and exact text of the error or warning message in your original question. This information may help readers determine the cause of the error and how to correct it more quickly. Thanks.

Answer 1

[Star Strider]

In the ‘D_i’ function, ‘c_i’ was originally missing its argument, and that threw the error.

Correcting that, and vectorising the exponentiations produces —

%%---------constants:
Gma_32 = 100;
Gma = 210e-15;
gamma_u = 500;
gamma_c = 50;
a = Gma_32/sqrt(2*gamma_u*Gma);
n = 4e10;
c1 = -4;
c2 = 2.05;
c3 = 1;
K = 10;



%--------Function
% 
% X = @(k) -4*n - a^2*n*sqrt(n) + 4*c1*k.^4 + (2*a*sqrt(n)-16*K^2 + 4*a*c1*c3*sqrt(n) + 8*n*c1*c2)*k.^2
% Sq = @(k) sqrt((-X(k) + sqrt(X(k).^2 + Y^2 ))/2)
% f = @(k) -2*k.^2 - 2*n - a*sqrt(n) + Sq(k)
% f2 = @(k) -2*k.^2 - 2*n - a*sqrt(n) - Sq(k)

%------------------------------Fns:
b_i = @(k) -4*c1*k*K;
b_r = @(k) 2*k.^2 +2*n + a*sqrt(n);

c_i = @(k) ( 4*n*c2* - 2*(2*n + a*sqrt(n))*c1 + 2*a*sqrt(n)*c3 )*K*k;
c_r = @(k) -(1 + c1^2)*k.^4 - (2*n -4*(1 + c1^2)*K^2 + sqrt(n)*c3*c1 + 2*n*c1*c2 )*k.^2;
 
D_r = @(k)  b_r(k).^2 - b_i(k).^2 -4*c_r(k);  
D_i = @(k)  2*b_i(k).*b_r(k) - 4*c_i(k);  

f = @(k) -b_i(k) + sqrt( -D_r(k) + sqrt(D_i(k).^2 + D_r(k).^2))/4;
 
%-------Grid:
k = -200:0.1:200;
% %-------Plot
% 

plot(k,f(k))

%plot(k,f2(k))

.

Answer 2

[Tlotlo Oepeng]

thank you

[Star Strider]

As always, my pleasure!