Q:

How to use conditions within an anonymous function

A function can be defined as @(x) x^.2 (for e.g)
But in case, we have a function that takes different representation on different intervals for e.g : if abs(x)<3 fun = x^.2 else 0 
How can we use the same way (i mean use @(x) ) to define such a function.  

A:

There's a few ways to do this. 
Multiply by false:
g = @(x) (abs(x)<3) .* x.^2

or define a proper function (the BEST way really):
function y = g(x)

    y = zeros(size(x), class(x));

    inds = abs(x)<3;
    y(inds) = x(inds).^2;

end 

or do the messy-ugly-inefficient-but-fun thing and use an inline-if:
iif = @(varargin) varargin{2 * find([varargin{1:2:end}], 1, 'first')}();
g = @(x) iff( ...
    abs(x)<3,  x.^2, ...
        true,  0);

