# [Numpy-tickets] [NumPy] #564: poly1d subtraction yields coefficient of 0

NumPy numpy-tickets@scipy....
Sun Aug 5 19:29:22 CDT 2007

```#564: poly1d subtraction yields coefficient of 0
-----------------------+----------------------------------------------------
Reporter:  DrIdiot    |       Owner:  somebody
Type:  defect     |      Status:  new
Priority:  normal     |   Milestone:
Component:  numpy.lib  |     Version:  none
Severity:  normal     |    Keywords:  poly1d
-----------------------+----------------------------------------------------
Using ipython -pylabs, explicitly setting the leading coefficient to 0
does this:

In [3]: a = numpy.poly1d([1,2,3])
In [4]: a[2] = 0
In [5]: print a
+ 2 x + 3
In [6]: a.coeffs
Out[6]: array([0, 2, 3])

Likewise,

In [10]: a = numpy.poly1d([1,2,3])
In [11]: a[2] = 0
In [12]: a[1] = 0
In [13]: print a
+ 3
In [14]: a.coeffs
Out[14]: array([0, 0, 3])

Likewise,
In [15]: a = numpy.poly1d([1,2,3])
In [16]: a[2] = 0
In [17]: a[1] = 0
In [18]: a[0] = 0
In [19]: print a

In [20]: a.coeffs
Out[20]: array([0, 0, 0])

(The correct behavior is:)
In [22]: a = numpy.poly1d([0])
In [23]: print a
0

I am running Gentoo Linux and numpy version 1.0.3

--
Ticket URL: <http://projects.scipy.org/scipy/numpy/ticket/564>
NumPy <http://projects.scipy.org/scipy/numpy>
The fundamental package needed for scientific computing with Python.
```