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clean -- Set to zero elements that are approximately zero

Synopsis

Description

If the input is a matrix or a ring element, then the result has the same type, where each real or complex number coefficient that is less than epsilon in absolute value is replaced with zero.

i1 : e = 1e-11;
i2 : M = random(RR^4,RR^4)

o2 = | .525767    .447525 .302281 .866251 |
     | .747244    .684343 .694299 .980637 |
     | .455885    .427993 .521386 .887344 |
     | .000444439 .111509 .265069 .757479 |

                4          4
o2 : Matrix RR    <--- RR
              53         53
i3 : M * (M + 1) + 1 - M^2 - M

o3 = | 1           0           0            -2.22045e-16 |
     | 0           1           1.11022e-16  1.11022e-16  |
     | 1.11022e-16 1.11022e-16 1            2.22045e-16  |
     | 0           0           -5.55112e-17 1            |

                4          4
o3 : Matrix RR    <--- RR
              53         53
i4 : clean_e oo

o4 = | 1 0 0 0 |
     | 0 1 0 0 |
     | 0 0 1 0 |
     | 0 0 0 1 |

                4          4
o4 : Matrix RR    <--- RR
              53         53
Cleaning a polynomial is a way to get rid of small terms.
i5 : CC[x];
i6 : f = product(5,j -> x - exp(2*pi*j*ii/5))

      5                                  4                   3     
o6 = x  + (2.22045e-16 - 1.11022e-16*ii)x  - 1.11022e-16*ii*x  + (-
     ------------------------------------------------------------------------
                                   2
     1.11022e-16 - 1.11022e-16*ii)x  - 1.11022e-16*ii*x - 1 + 5.55112e-16*ii

o6 : CC  [x]
       53
i7 : clean_e f  

      5
o7 = x  - 1

o7 : CC  [x]
       53

See also

Ways to use clean :