how to integrate a product with function handle

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Abhik Saha 2021-5-7

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编辑： Abhik Saha 2021-5-8

I want to perform a numerical integration with function handle. Please find details below

Nz = 256;

L = 1;

dz = L/Nz;

zgrid = dz*(0:Nz-1)'-L/2;

gN = 20000;

U0 = 5*gN;

U1=1.9*gN;

sigma = 5*dz;

xb = L/4;

tau = 0.01;

h=0.2*gN;

n0=mean(dens(abs(zgrid)<L/10,:));

wp=2*pi*sqrt(gN*n0);

Ub = @(t) U1*(t<tau)+(t>=tau)*(U1+h*sin(wp*(t-tau)));

Vext = @(t) (U0*exp(-(zgrid+xb).^2/sigma^2)+Ub(t)*exp(-(zgrid-xb).^2/sigma^2));

Now I want to integrate

integrate (Vext *A, zgrid)

where A is a double array matrix of dimension (zgrid,t)

The problem is Vext is function handle and A is numerical values of the dimension (zgrid,t). please help how to do this integration?

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Answer 1

Steven Lord 2021-5-7

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在 MATLAB Online 中打开

You can't calculate the product of a number and a function handle. What you can do instead is calculate the product of a number and the result of evaluating that function handle.

fh = @(x) x.^2;

This works and returns a number. It evaluates the function handle with x = 5 then multiplies that result by 2.

y1 = 2*fh(5)
y1 = 50

This works and returns another function handle that you can evaluate. Note that inside the function handle fh2 I evaluate fh at the value that was passed into fh2.

fh2 = @(x) 2*fh(x)
fh2 = function_handle with value:
    @(x)2*fh(x)
y2 = fh2(7) % Essentially the same as y1 (except with x = 7 instead of x = 5.)
y2 = 98

This does not work which is why I put it last.

y3 = 2*fh
Operator '*' is not supported for operands of type 'function_handle'.

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Abhik Saha 2021-5-8

编辑：Abhik Saha 2021-5-8

I understand your point of view. Then one of the possible gateway is to generate the dataset of Vext with dimension zgrid and t. I mean to say Vext(zgrid,t). I am new to matlab so I don't know how to do this can you please tell me how to generate this dataset where lets say zgrid is already defined and t=linspace(0,10,1000).

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