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realPartMatrix -- real part of a matrix over CC

Synopsis

Description

Given a complex matrix, this method returns a real matrix obtained by taking the real part of each entry. It leaves matrices over RR and QQ unchanged.

i1 : A = random(RR^3,RR^5)

o1 = | .892712 .632944  .89189  .775187 .0741835 |
     | .673395 .0258884 .231053 .909047 .808694  |
     | .29398  .714827  .461944 .314897 .362835  |

                3         5
o1 : Matrix RR    <-- RR
              53        53
 
i2 : A == realPartMatrix A

o2 = true
 
i3 : B = sub(A, CC)

o3 = | .892712 .632944  .89189  .775187 .0741835 |
     | .673395 .0258884 .231053 .909047 .808694  |
     | .29398  .714827  .461944 .314897 .362835  |

                3         5
o3 : Matrix CC    <-- CC
              53        53
 
i4 : C = realPartMatrix B

o4 = | .892712 .632944  .89189  .775187 .0741835 |
     | .673395 .0258884 .231053 .909047 .808694  |
     | .29398  .714827  .461944 .314897 .362835  |

                3         5
o4 : Matrix RR    <-- RR
              53        53
 
i5 : clean(1e-10, A - C) == 0

o5 = true
 
i6 : D = random(QQ^3, QQ^1)

o6 = | 7/10 |
     | 1/2  |
     | 7/10 |

              3       1
o6 : Matrix QQ  <-- QQ
 
i7 : D == realPartMatrix D

o7 = true

If the matrix is over a polynomial ring, but has entries defined over the base field (e.g., when taking coefficients), then it is necessary to substitute into the base field first:

i8 : R = CC[x,y]

o8 = R

o8 : PolynomialRing
 
i9 : f = random(2,R)
-- warning: experimental computation over inexact field begun
--          results not reliable (one warning given per session)

                             2                                         
o9 = (.0410167 + .951912*ii)x  + (.752574 + .424521*ii)x*y + (.641878 +
     ------------------------------------------------------------------------
                 2
     .267055*ii)y

o9 : R
 
i10 : C = last coefficients f

o10 = {2} | .0410167+.951912ii |
      {2} | .752574+.424521ii  |
      {2} | .641878+.267055ii  |

              3      1
o10 : Matrix R  <-- R
 
i11 : realPartMatrix sub(C, coefficientRing R)

o11 = | .0410167 |
      | .752574  |
      | .641878  |

                 3         1
o11 : Matrix RR    <-- RR
               53        53

See also

Ways to use realPartMatrix :

For the programmer

The object realPartMatrix is a method function.