8000 Merge pull request #13202 from mtmoncur/rotated-companion-matrix · numpy/numpy@167a31b · GitHub
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charrischarris
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Merge pull request #13202 from mtmoncur/rotated-companion-matrix
ENH: use rotated companion matrix to reduce error
2 parents 5c3cb43 + 732d52a commit 167a31b

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6 files changed

+12
-6
lines changed

6 files changed

+12
-6
lines changed

‎numpy/polynomial/chebyshev.py

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1743,7 +1743,8 @@ def chebroots(c):
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if len(c) == 2:
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return np.array([-c[0]/c[1]])
17451745

1746-
m = chebcompanion(c)
1746+
# rotated companion matrix reduces error
1747+
m = chebcompanion(c)[::-1,::-1]
17471748
r = la.eigvals(m)
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r.sort()
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return r

‎numpy/polynomial/hermite.py

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1476,7 +1476,8 @@ def hermroots(c):
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if len(c) == 2:
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return np.array([-.5*c[0]/c[1]])
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1479-
m = hermcompanion(c)
1479+
# rotated companion matrix reduces error
1480+
m = hermcompanion(c)[::-1,::-1]
14801481
r = la.eigvals(m)
14811482
r.sort()
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return r

‎numpy/polynomial/hermite_e.py

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1471,7 +1471,8 @@ def hermeroots(c):
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if len(c) == 2:
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return np.array([-c[0]/c[1]])
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1474-
m = hermecompanion(c)
1474+
# rotated companion matrix reduces error
1475+
m = hermecompanion(c)[::-1,::-1]
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r = la.eigvals(m)
14761477
r.sort()
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return r

‎numpy/polynomial/laguerre.py

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1475,7 +1475,8 @@ def lagroots(c):
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if len(c) == 2:
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return np.array([1 + c[0]/c[1]])
14771477

1478-
m = lagcompanion(c)
1478+
# rotated companion matrix reduces error
1479+
m = lagcompanion(c)[::-1,::-1]
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r = la.eigvals(m)
14801481
r.sort()
14811482
return r

‎numpy/polynomial/legendre.py

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1505,7 +1505,8 @@ def legroots(c):
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if len(c) == 2:
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return np.array([-c[0]/c[1]])
15071507

1508-
m = legcompanion(c)
1508+
# rotated companion matrix reduces error
1509+
m = legcompanion(c)[::-1,::-1]
15091510
r = la.eigvals(m)
15101511
r.sort()
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return r

‎numpy/polynomial/polynomial.py

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1428,7 +1428,8 @@ def polyroots(c):
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if len(c) == 2:
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return np.array([-c[0]/c[1]])
14301430

1431-
m = polycompanion(c)
1431+
# rotated companion matrix reduces error
1432+
m = polycompanion(c)[::-1,::-1]
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r = la.eigvals(m)
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r.sort()
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return r

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