[Numpy-discussion] Nonzero behaving strangely?
santhu kumar
mesanthu at gmail.com
Thu Mar 17 22:10:21 EDT 2011
Thanks a lot for the replies.
I have misunderstood the output. When it says (array[0]), i thought it did
not find anything as opposed to the zeroth row. (Still getting used to
matlab indexing i guess !! ) .. Sorry !!
Thanks a lot for the sugestions though, Would keep it in mind ..
From: santhu kumar <mesanthu at gmail.com>
> Subject: [Numpy-discussion] Nonzero behaving strangely?
> To: numpy-discussion at scipy.org
> Message-ID:
> <AANLkTinnFb6cbRUDb3GuaQsMCoq0DKyWQy77j9HmMjxf at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hello all,
>
> I am new to Numpy. I used to program before in matlab and am getting used
> to
> Numpy.
>
> I have a array like:
> res
> array([[ 33.35053669, 49.4615004 , 44.27631299, 1. , 2.
> ],
> [ 32.84263059, 50.24752036, 43.92291659, 1. , 0.
> ],
> [ 33.68999668, 48.90554673, 43.51746687, 1. , 0.
> ],
> [ 34.11564931, 49.77487763, 44.83843076, 1. , 0.
> ],
> [ 32.4641859 , 48.65469145, 45.09300791, 1. , 3.
> ],
> [ 32.15428526, 49.26922262, 45.92959026, 1. , 0.
> ],
> [ 31.23860825, 48.21824628, 44.30816331, 1. , 0.
> ],
> [ 30.71171138, 47.45600573, 44.9282456 , 1. , 0.
> ],
> [ 30.53843426, 49.07713258, 44.20899822, 1. , 0.
> ],
> [ 31.54722284, 47.61953925, 42.95235178, 1. , 0.
> ],
> [ 32.44334635, 48.10500653, 42.51103537, 1. , 0.
> ],
> [ 31.77269609, 46.53603145, 43.06468455, 1. , 0.
> ],
> [ 30.1820843 , 47.80819604, 41.77667819, 1. , 0.
> ],
> [ 30.78652668, 46.82907769, 40.38586451, 1. , 0.
> ],
> [ 30.05963091, 46.84268609, 39.54583693, 1. , 0.
> ],
> [ 31.75239177, 47.22768463, 40.00717713, 1. , 0.
> ],
> [ 30.94617127, 45.76986265, 40.68226643, 1. , 0.
> ],
> [ 33.20069679, 47.42127403, 45.66738249, 1. , 0.
> ],
> [ 34.39608116, 47.25481126, 45.4438599 , 1. , 0.
> ]])
>
> The array is 19X5.
> When I do:
> nid = (res[:,4]==2).nonzero()
> nid tuple turns out to be empty. But the very first row satisfies the
> criteria.
>
> nid = (res[:,4]==3).nonzero(), works out and finds the 5th row.
>
> Am i doing something wrong?
> I basically want to find the rows whose fifth coloumn(4th in numpy matrix
> format) is 2.
>
> Any suggestions?
> Thanks
> Santhosh
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> ------------------------------
>
> Message: 2
> Date: Thu, 17 Mar 2011 23:19:42 +0100
> From: Matthieu Brucher <matthieu.brucher at gmail.com>
> Subject: Re: [Numpy-discussion] Nonzero behaving strangely?
> To: Discussion of Numerical Python <numpy-discussion at scipy.org>
> Message-ID:
> <AANLkTimEipz6cPaMauY2f_0MpJwkWjdWe0OC4WM-LpOu at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi,
>
> Did you try np.where(res[:,4]==2) ?
>
> Matthieu
>
> 2011/3/17 santhu kumar <mesanthu at gmail.com>
>
> > Hello all,
> >
> > I am new to Numpy. I used to program before in matlab and am getting used
> > to Numpy.
> >
> > I have a array like:
> > res
> > array([[ 33.35053669, 49.4615004 , 44.27631299, 1. , 2.
> > ],
> > [ 32.84263059, 50.24752036, 43.92291659, 1. , 0.
> > ],
> > [ 33.68999668, 48.90554673, 43.51746687, 1. , 0.
> > ],
> > [ 34.11564931, 49.77487763, 44.83843076, 1. , 0.
> > ],
> > [ 32.4641859 , 48.65469145, 45.09300791, 1. , 3.
> > ],
> > [ 32.15428526, 49.26922262, 45.92959026, 1. , 0.
> > ],
> > [ 31.23860825, 48.21824628, 44.30816331, 1. , 0.
> > ],
> > [ 30.71171138, 47.45600573, 44.9282456 , 1. , 0.
> > ],
> > [ 30.53843426, 49.07713258, 44.20899822, 1. , 0.
> > ],
> > [ 31.54722284, 47.61953925, 42.95235178, 1. , 0.
> > ],
> > [ 32.44334635, 48.10500653, 42.51103537, 1. , 0.
> > ],
> > [ 31.77269609, 46.53603145, 43.06468455, 1. , 0.
> > ],
> > [ 30.1820843 , 47.80819604, 41.77667819, 1. , 0.
> > ],
> > [ 30.78652668, 46.82907769, 40.38586451, 1. , 0.
> > ],
> > [ 30.05963091, 46.84268609, 39.54583693, 1. , 0.
> > ],
> > [ 31.75239177, 47.22768463, 40.00717713, 1. , 0.
> > ],
> > [ 30.94617127, 45.76986265, 40.68226643, 1. , 0.
> > ],
> > [ 33.20069679, 47.42127403, 45.66738249, 1. , 0.
> > ],
> > [ 34.39608116, 47.25481126, 45.4438599 , 1. , 0.
> > ]])
> >
> > The array is 19X5.
> > When I do:
> > nid = (res[:,4]==2).nonzero()
> > nid tuple turns out to be empty. But the very first row satisfies the
> > criteria.
> >
> > nid = (res[:,4]==3).nonzero(), works out and finds the 5th row.
> >
> > Am i doing something wrong?
> > I basically want to find the rows whose fifth coloumn(4th in numpy matrix
> > format) is 2.
> >
> > Any suggestions?
> > Thanks
> > Santhosh
> >
> > _______________________________________________
> > NumPy-Discussion mailing list
> > NumPy-Discussion at scipy.org
> > http://mail.scipy.org/mailman/listinfo/numpy-discussion
> >
> >
>
>
> --
> Information System Engineer, Ph.D.
> Blog: http://matt.eifelle.com
> LinkedIn: http://www.linkedin.com/in/matthieubrucher
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>
> ------------------------------
>
> Message: 4
> Date: Thu, 17 Mar 2011 17:27:19 -0500
> From: Warren Weckesser <warren.weckesser at enthought.com>
> Subject: Re: [Numpy-discussion] Nonzero behaving strangely?
> To: Discussion of Numerical Python <numpy-discussion at scipy.org>
> Message-ID:
> <AANLkTi=SHeodTbnqe07Gco1F4wYeQzOOjTyi6n-qia-g at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> On Thu, Mar 17, 2011 at 5:17 PM, santhu kumar <mesanthu at gmail.com> wrote:
>
> > Hello all,
> >
> > I am new to Numpy. I used to program before in matlab and am getting used
> > to Numpy.
> >
> > I have a array like:
> > res
> > array([[ 33.35053669, 49.4615004 , 44.27631299, 1. , 2.
> > ],
> > [ 32.84263059, 50.24752036, 43.92291659, 1. , 0.
> > ],
> > [ 33.68999668, 48.90554673, 43.51746687, 1. , 0.
> > ],
> > [ 34.11564931, 49.77487763, 44.83843076, 1. , 0.
> > ],
> > [ 32.4641859 , 48.65469145, 45.09300791, 1. , 3.
> > ],
> > [ 32.15428526, 49.26922262, 45.92959026, 1. , 0.
> > ],
> > [ 31.23860825, 48.21824628, 44.30816331, 1. , 0.
> > ],
> > [ 30.71171138, 47.45600573, 44.9282456 , 1. , 0.
> > ],
> > [ 30.53843426, 49.07713258, 44.20899822, 1. , 0.
> > ],
> > [ 31.54722284, 47.61953925, 42.95235178, 1. , 0.
> > ],
> > [ 32.44334635, 48.10500653, 42.51103537, 1. , 0.
> > ],
> > [ 31.77269609, 46.53603145, 43.06468455, 1. , 0.
> > ],
> > [ 30.1820843 , 47.80819604, 41.77667819, 1. , 0.
> > ],
> > [ 30.78652668, 46.82907769, 40.38586451, 1. , 0.
> > ],
> > [ 30.05963091, 46.84268609, 39.54583693, 1. , 0.
> > ],
> > [ 31.75239177, 47.22768463, 40.00717713, 1. , 0.
> > ],
> > [ 30.94617127, 45.76986265, 40.68226643, 1. , 0.
> > ],
> > [ 33.20069679, 47.42127403, 45.66738249, 1. , 0.
> > ],
> > [ 34.39608116, 47.25481126, 45.4438599 , 1. , 0.
> > ]])
> >
> > The array is 19X5.
> > When I do:
> > nid = (res[:,4]==2).nonzero()
> > nid tuple turns out to be empty. But the very first row satisfies the
> > criteria.
> >
> > nid = (res[:,4]==3).nonzero(), works out and finds the 5th row.
> >
> > Am i doing something wrong?
> > I basically want to find the rows whose fifth coloumn(4th in numpy matrix
> > format) is 2.
> >
> >
>
> Are you sure the value of res[0,4] is *exactly* 2.0, and not something
> like,
> say, 2.0000000000000009?
>
> Warren
>
>
> > Any suggestions?
> > Thanks
> > Santhosh
> >
> > _______________________________________________
> > NumPy-Discussion mailing list
> > NumPy-Discussion at scipy.org
> > http://mail.scipy.org/mailman/listinfo/numpy-discussion
> >
> >
>
>
>
>
> ------------------------------
>
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> NumPy-Discussion at scipy.org
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>
>
> End of NumPy-Discussion Digest, Vol 54, Issue 75
> ************************************************
>
--
bye and take care
santhu
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