fimplicit gives a warning ''Function behaves unexpectedly on array inputs.''

I just wanna plot a dispersion equation according to the paper.

here is my code, really simple.

clc,clear all,

fimplicit(@(x,y) 9*y^4-((1-9)*9+2*9^2*10*(1-cos(x)))*y^2+2*9^2*10*(1-cos(x)),[-3 3 0 20]);

But the plot is not accurate near 0. What is going on and how can I fix it？

Warning message:

Warning: Function behaves unexpectedly on array inputs. To improve

performance, properly vectorize your function to return an output

with the same size and shape as the input arguments.

> In matlab.graphics.function.ImplicitFunctionLine>getFunction

In matlab.graphics.function.ImplicitFunctionLine/updateFunction

In matlab.graphics.function.ImplicitFunctionLine/set.Function_I

In matlab.graphics.function.ImplicitFunctionLine/set.Function

In matlab.graphics.function.ImplicitFunctionLine

In fimplicit>singleFimplicit (line 185)

In fimplicit>@(f)singleFimplicit(cax,f,limits,extraOpts,args) (line 148)

In fimplicit>vectorizeFimplicit (line 148)

In fimplicit (line 126)

In Test (line 2)

>>

[sajid majeed]

fp = fimplicit(@(q,E) gamma(1/4-E/2).*hypergeom(1/4-E/2,1/2,q.^2) - 2*gamma(3/4-E/2).*hypergeom(3/4-E/2,3/2,q.^2).*q);

This is my code but errors occur. i.e.

Warning: Function behaves unexpectedly on array inputs. To improve performance, properly vectorize your function to return an output with the same size and

shape as the input arguments. > In matlab.graphics.function.ImplicitFunctionLine>getFunction

In matlab.graphics.function/ImplicitFunctionLine/updateFunction

In matlab.graphics.function/ImplicitFunctionLine/set.Function_I

In matlab.graphics.function/ImplicitFunctionLine/set.Function

In matlab.graphics.function.ImplicitFunctionLine

In fimplicit>singleFimplicit (line 193)

In fimplicit>@(f)singleFimplicit(cax,f,limits,extraOpts,args) (line 152)

In fimplicit>vectorizeFimplicit (line 152)

In fimplicit (line 126)

In tuntitled (line 1)

can any one please guide me

[Walter Roberson]

@sajid majeed

The difficulty is that hypergeom expects vectors for the first two parameters. The vectors control what is to be calculated, and the calculation is vectorized only with respect to the third parameter. For example, hypergeom([1 2], 1/2, 1/3) is not at all the same as [hypergeom([1], 1/2, 1/3), hypergeom([2], 1/2, 1/3)]

When fimplicit is called, it expects the function to be vectorized with respect to both parameters -- it expects that fun(A,B) is the same as [fun(A(1),B(1)), fun(A(2),B(2)), ...] But since vectors for the first two parameters change what is calculated for hypergeom, hypergeom(A,1/2,q) for vector A is not the same as [hypergeom(A(1),1/2,q(1)), hypergeom(A(2),1/2,q(2))...]

fimplicit specifcally probes to ensure that the function is properly vectorized... and your function fails because of way hypergeom is used.

You will need to manually vectorize, such as

arrayfun(@(e,Q) hypergeom(1/4-e/2,1/2,Q.^2), E, q)

instead of hypergeom(1/4-E,1/2,q.^2)

Answer 1

[Walter Roberson]

vectorize your function . use .* instead of * and use .^ instead of ^

[Yixin Yao]

Thanks, it works.