Complex(3) User Contributed Perl Documentation Complex(3)
NAME
PDL::Complex - handle complex numbers
SYNOPSIS
use PDL;
use PDL::Complex;
DESCRIPTION
This module features a growing number of functions manipulating complex numbers. These are usually represented as a pair "[ real imag ]" or
"[ angle phase ]". If not explicitly mentioned, the functions can work inplace (not yet implemented!!!) and require rectangular form.
While there is a procedural interface available ("$a/$b*$c <=" Cmul (Cdiv $a, $b), $c)>), you can also opt to cast your pdl's into the
"PDL::Complex" datatype, which works just like your normal piddles, but with all the normal perl operators overloaded.
The latter means that "sin($a) + $b/$c" will be evaluated using the normal rules of complex numbers, while other pdl functions (like "max")
just treat the piddle as a real-valued piddle with a lowest dimension of size 2, so "max" will return the maximum of all real and imaginary
parts, not the "highest" (for some definition)
TIPS, TRICKS &; CAVEATS
o "i" is a constant exported by this module, which represents "-1**0.5", i.e. the imaginary unit. it can be used to quickly and con-
viniently write complex constants like this: "4+3*i".
o Use "r2C(real-values)" to convert from real to complex, as in "$r = Cpow $cplx, r2C 2". The overloaded operators automatically do that
for you, all the other functions, do not. So "Croots 1, 5" will return all the fifths roots of 1+1*i (due to threading).
o use "cplx(real-valued-piddle)" to cast from normal piddles intot he complex datatype. Use "real(complex-valued-piddle)" to cast back.
This requires a copy, though.
o BEWARE: This module has not been extensively tested. Watch out and send me bugreports!
EXAMPLE WALK-THROUGH
The complex constant five is equal to "pdl(1,0)":
perldl> p $x = r2C 5
[5 0]
Now calculate the three roots of of five:
perldl> p $r = Croots $x, 3
[
[ 1.7099759 0]
[-0.85498797 1.4808826]
[-0.85498797 -1.4808826]
]
Check that these really are the roots of unity:
perldl> p $r ** 3
[
[ 5 0]
[ 5 -3.4450524e-15]
[ 5 -9.8776239e-15]
]
Duh! Could be better. Now try by multiplying $r three times with itself:
perldl> p $r*$r*$r
[
[ 5 0]
[ 5 -2.8052647e-15]
[ 5 -7.5369398e-15]
]
Well... maybe "Cpow" (which is used by the "**" operator) isn't as bad as I thought. Now multiply by "i" and negate, which is just a very
expensive way of swapping real and imaginary parts.
perldl> p -($r*i)
[
[ -0 1.7099759]
[ 1.4808826 -0.85498797]
[ -1.4808826 -0.85498797]
]
Now plot the magnitude of (part of) the complex sine. First generate the coefficients:
perldl> $sin = i * zeroes(50)->xlinvals(2,4)
+ zeroes(50)->xlinvals(0,7)
Now plot the imaginary part, the real part and the magnitude of the sine into the same diagram:
perldl> line im sin $sin; hold
perldl> line re sin $sin
perldl> line abs sin $sin
Sorry, but I didn't yet try to reproduce the diagram in this text. Just run the commands yourself, making sure that you have loaded
"PDL::Complex" (and "PDL::Graphics::PGPLOT").
FUNCTIONS
cplx real-valued-pdl
Cast a real-valued piddle to the complex datatype. The first dimension of the piddle must be of size 2. After this the usual (complex)
arithmetic operators are applied to this pdl, rather than the normal elementwise pdl operators. Dataflow to the complex parent works. Use
"sever" on the result if you don't want this.
real cplx-valued-pdl
Cast a complex vlaued pdl back to the "normal" pdl datatype. Afterwards the normal elementwise pdl operators are used in operations.
Dataflow to the real parent works. Use "sever" on the result if you don't want this.
r2C
Signature: (r(); [o]c(m=2))
convert real to complex, assuming an imaginary part of zero
i2C
Signature: (r(); [o]c(m=2))
convert imaginary to complex, assuming a real part of zero
Cr2p
Signature: (r(m=2); float+ [o]p(m=2))
convert complex numbers in rectangular form to polar (mod,arg) form
Cp2r
Signature: (r(m=2); [o]p(m=2))
convert complex numbers in polar (mod,arg) form to rectangular form
Cmul
Signature: (a(m=2); b(m=2); [o]c(m=2))
complex multiplication
Cscale
Signature: (a(m=2); b(); [o]c(m=2))
mixed complex/real multiplication
Cdiv
Signature: (a(m=2); b(m=2); [o]c(m=2))
complex division
Ccmp
Signature: (a(m=2); b(m=2); [o]c())
Complex comparison oeprator (spaceship). It orders by real first, then by imaginary.
Cconj
Signature: (a(m=2); [o]c(m=2))
complex conjugation
Cabs
Signature: (a(m=2); [o]c())
complex "abs()" (also known as modulus)
Cabs2
Signature: (a(m=2); [o]c())
complex squared "abs()" (also known squared modulus)
Carg
Signature: (a(m=2); [o]c())
complex argument function ("angle")
Csin
Signature: (a(m=2); [o]c(m=2))
sin (a) = 1/(2*i) * (exp (a*i) - exp (-a*i))
Ccos
Signature: (a(m=2); [o]c(m=2))
cos (a) = 1/2 * (exp (a*i) + exp (-a*i))
Ctan a [not inplace]
tan (a) = -i * (exp (a*i) - exp (-a*i)) / (exp (a*i) + exp (-a*i))
Cexp
Signature: (a(m=2); [o]c(m=2))
exp (a) = exp (real (a)) * (cos (imag (a)) + i * sin (imag (a)))
Clog
Signature: (a(m=2); [o]c(m=2))
log (a) = log (cabs (a)) + i * carg (a)
Cpow
Signature: (a(m=2); b(m=2); [o]c(m=2))
complex "pow()" ("**"-operator)
Csqrt
Signature: (a(m=2); [o]c(m=2))
Casin
Signature: (a(m=2); [o]c(m=2))
Cacos
Signature: (a(m=2); [o]c(m=2))
Catan cplx [not inplace]
Return the complex "atan()".
Csinh
Signature: (a(m=2); [o]c(m=2))
sinh (a) = (exp (a) - exp (-a)) / 2
Ccosh
Signature: (a(m=2); [o]c(m=2))
cosh (a) = (exp (a) + exp (-a)) / 2
Ctanh
Signature: (a(m=2); [o]c(m=2))
Casinh
Signature: (a(m=2); [o]c(m=2))
Cacosh
Signature: (a(m=2); [o]c(m=2))
Catanh
Signature: (a(m=2); [o]c(m=2))
Cproj
Signature: (a(m=2); [o]c(m=2))
compute the projection of a complex number to the riemann sphere
Croots
Signature: (a(m=2); [o]c(m=2,n); int n => n)
Compute the "n" roots of "a". "n" must be a positive integer. The result will always be a complex type!
re cplx, im cplx
Return the real or imaginary part of the complex number(s) given. These are slicing operators, so data flow works. The real and imaginary
parts are returned as piddles (ref eq PDL).
rCpolynomial
Signature: (coeffs(n); x(c=2,m); [o]out(c=2,m))
evaluate the polynomial with (real) coefficients "coeffs" at the (complex) position(s) "x". "coeffs[0]" is the constant term.
AUTHOR
Copyright (C) 2000 Marc Lehmann <pcg@goof.com>. All rights reserved. There is no warranty. You are allowed to redistribute this software /
documentation as described in the file COPYING in the PDL distribution.
SEE ALSO
perl(1), PDL.
perl v5.8.0 2003-01-29 Complex(3)