Distributions
We represent distributions as a complex function in the limit
where the imaginary part goes to 0. Signum (sign), delta and
doublet functions arise from the derivative of the absolute value
function with respect to its real part.
Ref.
Use definition of conjugate and derivative of abs(x) from SandBoxFunctionalSpecialFunction?
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)lib FSPECX
FunctionalSpecialFunction is now explicitly exposed in frame initial
FunctionalSpecialFunction will be automatically loaded when needed
from /var/aw/var/LatexWiki/FSPECX.NRLIB/FSPECX
wirtingerD(ex,z) == eval(D(eval(ex,z=%conjugate),%conjugate),%conjugate=z)
Type: Void
Absolute value as a function of real or complex variables
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abs(z:Expression Integer):Expression Integer == sqrt(z*conjugate(z)); abs(z)
Function declaration abs : Expression(Integer) -> Expression(Integer
) has been added to workspace.
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Compiling function abs with type Expression(Integer) -> Expression(
Integer)
Type: Expression(Integer)
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abz(a:Expression Integer):Expression Integer == sqrt((a+%i*b)*(a-%i*b)); abz(x)
Function declaration abz : Expression(Integer) -> Expression(Integer
) has been added to workspace.
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Compiling function abz with type Expression(Integer) -> Expression(
Integer)
Type: Expression(Integer)
Total Wirtinger derivatives of this complex function (CR-calculus)
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abs':=wirtingerD(abs(z),z)+wirtingerD(abs(z),conjugate z)
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Compiling function wirtingerD with type (Expression(Integer),
Variable(z)) -> Expression(Integer)
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Compiling function wirtingerD with type (Expression(Integer),
Expression(Integer)) -> Expression(Integer)
Type: Expression(Integer)
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abs'':=wirtingerD(abs',z)+wirtingerD(abs',conjugate z)
Type: Expression(Integer)
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abs''':=wirtingerD(abs'',z)+wirtingerD(abs'',conjugate z)
Type: Expression(Integer)
Consider these as complex functions of for real and .
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realSignum:Expression Integer:=eval(eval(abs',z=a+%i*b),[conjugate(a)=a,conjugate(b)=b])
Type: Expression(Integer)
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test(realSignum=D(abz(a),a))
Type: Boolean
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signum(x)==eval(realSignum,a=x); signum(x)
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Compiling function signum with type Variable(x) -> Expression(
Integer)
Type: Expression(Integer)
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--
realDirac:Expression Integer:=eval(eval(abs'',z=a+%i*b),[conjugate(a)=a,conjugate(b)=b])
Type: Expression(Integer)
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test(realDirac=D(abz(a),[a,a]))
Type: Boolean
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diracDelta(x)==eval(realDirac/2,a=x); diracDelta(x)
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Compiling function diracDelta with type Variable(x) -> Expression(
Integer)
Type: Expression(Integer)
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--
realUnitDoublet:Expression Integer:=eval(eval(abs''',z=a+%i*b),[conjugate(a)=a,conjugate(b)=b])
Type: Expression(Integer)
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test(realUnitDoublet=D(abz(a),[a,a,a]))
Type: Boolean
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unitDoublet(x)==eval(-realUnitDoublet/2,a=x); unitDoublet(x)
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Compiling function unitDoublet with type Variable(x) -> Expression(
Integer)
Type: Expression(Integer)
We are interested in the behavior of these functions in the limit as
.
signum Properties
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limit( signum(1) ,b=0)
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Compiling function signum with type PositiveInteger -> Expression(
Integer)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( signum(-1) ,b=0)
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Compiling function signum with type Integer -> Expression(Integer)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( signum(0) ,b=0)
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Compiling function signum with type NonNegativeInteger -> Expression
(Integer)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( signum(x)^2 ,b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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-- odd function
test( signum(x)=-signum(-x))
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Compiling function signum with type Polynomial(Integer) ->
Expression(Integer)
Type: Boolean
diracDelta Properties
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limit( diracDelta(1) ,b=0)
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Compiling function diracDelta with type PositiveInteger ->
Expression(Integer)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( diracDelta(-1) ,b=0)
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Compiling function diracDelta with type Integer -> Expression(
Integer)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( diracDelta(0) ,b=0)
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Compiling function diracDelta with type NonNegativeInteger ->
Expression(Integer)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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-- even function
test( diracDelta(x)=diracDelta(-x) )
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Compiling function diracDelta with type Polynomial(Integer) ->
Expression(Integer)
Type: Boolean
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limit( diracDelta(x)^2 ,b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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integrate(diracDelta(x),x=%minusInfinity..%plusInfinity,"noPole")
Type: Union(f1: OrderedCompletion
?(Expression(Integer)),
...)
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f(x)==c1*x+c2
Type: Void
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test(integrate(f(x)*diracDelta(x-t),x=%minusInfinity..%plusInfinity,"noPole")=f(t))
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Compiling function f with type Variable(x) -> Polynomial(Integer)
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Compiling function f with type Variable(t) -> Polynomial(Integer)
Type: Boolean
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limit(integrate(log(x)*diracDelta(x-t),x=%minusInfinity..%plusInfinity,"noPole"), b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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eval(%,t=exp(x))
Type: Expression(Integer)
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integrate(diracDelta(2*x),x=%minusInfinity..%plusInfinity,"noPole")
Type: Union(f1: OrderedCompletion
?(Expression(Integer)),
...)
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--
limit( signum(x)*diracDelta(x) ,b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit(diracDelta(x^2), b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
The Unit Doublet function comes after diracDelta
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test(unitDoublet(x)=3*diracDelta(x)*signum(x)/abz(x))
Type: Boolean
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limit( unitDoublet(1) ,b=0)
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Compiling function unitDoublet with type PositiveInteger ->
Expression(Integer)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( unitDoublet(-1) ,b=0)
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Compiling function unitDoublet with type Integer -> Expression(
Integer)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( unitDoublet(0) ,b=0)
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Compiling function unitDoublet with type NonNegativeInteger ->
Expression(Integer)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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-- odd function
test( unitDoublet(x)=-unitDoublet(-x) )
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Compiling function unitDoublet with type Polynomial(Integer) ->
Expression(Integer)
Type: Boolean
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limit( unitDoublet(x)^2 ,b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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integrate(unitDoublet(x),x=%minusInfinity..%plusInfinity,"noPole")
Type: Union(f1: OrderedCompletion
?(Expression(Integer)),
...)
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f(x)==c1*x^2+c2*x+c3
Compiled code for f has been cleared.
1 old definition(s) deleted for function or rule f
Type: Void
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test(integrate(f(x)*unitDoublet(x-t),x=%minusInfinity..%plusInfinity,"noPole")=eval(D(f(x),x),x=t))
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Compiling function f with type Variable(x) -> Polynomial(Integer)
Type: Boolean
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integrate(unitDoublet(2*x),x=%minusInfinity..%plusInfinity,"noPole")
Type: Union(f1: OrderedCompletion
?(Expression(Integer)),
...)
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--
limit( signum(x)*unitDoublet(x) ,b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( diracDelta(x)*unitDoublet(x) ,b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( unitDoublet(x^2) ,b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
Heaviside
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realHeaviside:=integrate(diracDelta(a),a)
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Compiling function diracDelta with type Variable(a) -> Expression(
Integer)
Type: Union(Expression(Integer),...)
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heavisideStep(x)==eval(realHeaviside,a=x)
Type: Void
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limit( heavisideStep(1), b=0)
There are 12 exposed and 6 unexposed library operations named eval
having 2 argument(s) but none was determined to be applicable.
Use HyperDoc Browse, or issue
)display op eval
to learn more about the available operations. Perhaps
package-calling the operation or using coercions on the arguments
will allow you to apply the operation.
Cannot find a definition or applicable library operation named eval
with argument type(s)
Union(Expression(Integer),List(Expression(Integer)))
Equation(Polynomial(Integer))
Perhaps you should use "@" to indicate the required return type,
or "$" to specify which version of the function you need.
FriCAS will attempt to step through and interpret the code.
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( heavisideStep(-1) ,b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( heavisideStep(0) ,b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( heavisideStep(x), x=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( heavisideStep(x) ,x=%plusInfinity)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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limit( heavisideStep(x) ,x=%minusInfinity)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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test(simplify( (1+signum(x))/2 - heavisideStep(x) ) = 0)
Type: Boolean
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test(limit( integrate(heavisideStep(t),t=%minusInfinity..x, "noPole") - x*heavisideStep(x), b=0) =0)
Type: Boolean
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-- diracDelta?
d1:=integrate(heavisideStep(t)*unitDoublet(t),t=%minusInfinity..x, "noPole")
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Compiling function unitDoublet with type Variable(t) -> Expression(
Integer)
Type: Union(f1: OrderedCompletion
?(Expression(Integer)),
...)
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simplify(d1-diracDelta(x))
Type: Expression(Integer)
Problems?
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-- expected 1/abs(c)
integrate(diracDelta(c*x),x=%minusInfinity..%plusInfinity,"noPole")
Type: Union(f1: OrderedCompletion
?(Expression(Integer)),
...)
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f(x)==c1*x^2+c2*x+c3
Compiled code for f has been cleared.
1 old definition(s) deleted for function or rule f
Type: Void
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integrate(f(x)*diracDelta(x-t),x=%minusInfinity..%plusInfinity,"noPole")
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Compiling function f with type Variable(x) -> Polynomial(Integer)
Type: Union(fail: failed,...)
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-- expected
f(t)
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Compiling function f with type Variable(t) -> Polynomial(Integer)
Type: Polynomial(Integer)
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-- expected 1
integrate(exp(x)*diracDelta(x),x=%minusInfinity..%plusInfinity,"noPole")
Type: Union(fail: failed,...)
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-- expected 1
integrate(exp(x)*unitDoublet(x),x=%minusInfinity..%plusInfinity,"noPole")
Type: Union(fail: failed,...)
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-- loops forever on %plusInfinity limit of indefinite integral
--integrate(log(x)*unitDoublet(x-t),x=%minusInfinity..%plusInfinity,"noPole")
-- expected x*abs(x)/2
integrate(abs(x),x)
Type: Union(Expression(Integer),...)
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integrate(abz(x),x)
Type: Union(Expression(Integer),...)
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limit(%,b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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-- expected abs(x)
integrate(abs',z)
Type: Union(Expression(Integer),...)
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integrate(signum(x),x)
Type: Union(Expression(Integer),...)
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limit(%,b=0)
Type: Union(OrderedCompletion
?(Expression(Integer)),
...)
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-- expected signum(x)/2
integrate(abs'',z)
Type: Union(Expression(Integer),...)
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integrate(diracDelta(x^2+y^2), x=%minusInfinity..%plusInfinity, "noPole")
Type: Union(fail: failed,...)
Convolution
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g(x)==abz(x)/2; g(y)
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Compiling function g with type Variable(y) -> Expression(Integer)
Type: Expression(Integer)
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h(x)==heavisideStep(x+1/2)-heavisideStep(x-1/2); h(x)
Cannot compile map: heavisideStep
We will attempt to interpret the code.
Type: Expression(Integer)
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conv:=integrate(h(x-y)*g(y),y=%minusInfinity..%plusInfinity,"noPole")
Type: Union(fail: failed,...)
Representing a distribution as a series of bump functions
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)lib GDRAW
GnuDraw is now explicitly exposed in frame initial
GnuDraw will be automatically loaded when needed from
/var/aw/var/LatexWiki/GDRAW.NRLIB/GDRAW
X:=[(x/10)::DFLOAT for x in -100..100 by 1];
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Y:=[eval(unitDoublet(x),b=1.0)::DFLOAT for x in X];
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Compiling function unitDoublet with type DoubleFloat -> Expression(
DoubleFloat)
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gnuDraw(X,Y,"SandBoxDiracDeltaX2.dat")
Graph data being transmitted to the viewport manager...
FriCAS2D data being transmitted to the viewport manager...
Type: Void