[Numpy-discussion] Compound conditional indexing
Hello, How to conditionally index an array as shown below : a = arange(10) a[5a8] to get array([6,7]) I can't do this with where either. What is the cure for this? Thanks. -- Gökhan ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] Compound conditional indexing
There may be a more elegant way, but: In [2]: a = np.arange(10) In [3]: a[(a5) (a8)] Out[3]: array([6, 7]) On Wed, Sep 30, 2009 at 1:27 PM, Gökhan Sever gokhanse...@gmail.com wrote: Hello, How to conditionally index an array as shown below : a = arange(10) a[5a8] to get array([6,7]) I can't do this with where either. What is the cure for this? Thanks. -- Gökhan ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] Compound conditional indexing
Gökhan Sever wrote: How to conditionally index an array as shown below : a = arange(10) a[5a8] to get array([6,7]) In [56]: a[(5a) (a8)] Out[56]: array([6, 7]) not as efficient as it might be, but it works. -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/ORR(206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception chris.bar...@noaa.gov ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] Compound conditional indexing
Thanks this works. My second question how to access a second array using this condition? I am trying slice another array using a compound condition on the reference array. say: a = 1,2,3,4,5, b = 20,30,40,50,60 I want to get elements of a only when a = 3,4. I know I need indices but how ? On Wed, Sep 30, 2009 at 1:32 PM, Joe Kington jking...@wisc.edu wrote: There may be a more elegant way, but: In [2]: a = np.arange(10) In [3]: a[(a5) (a8)] Out[3]: array([6, 7]) On Wed, Sep 30, 2009 at 1:27 PM, Gökhan Sever gokhanse...@gmail.comwrote: Hello, How to conditionally index an array as shown below : a = arange(10) a[5a8] to get array([6,7]) I can't do this with where either. What is the cure for this? Thanks. -- Gökhan ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion -- Gökhan ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] Compound conditional indexing
On Wed, Sep 30, 2009 at 14:40, Gökhan Sever gokhanse...@gmail.com wrote: Thanks this works. My second question how to access a second array using this condition? I am trying slice another array using a compound condition on the reference array. say: a = 1,2,3,4,5, b = 20,30,40,50,60 I want to get elements of a only when a = 3,4. I know I need indices but how ? Did you mean elements of b only where a = 3,4? b[(a==3) | (a==4)] -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] Compound conditional indexing
On Wed, Sep 30, 2009 at 2:45 PM, Robert Kern robert.k...@gmail.com wrote: On Wed, Sep 30, 2009 at 14:40, Gökhan Sever gokhanse...@gmail.com wrote: Thanks this works. My second question how to access a second array using this condition? I am trying slice another array using a compound condition on the reference array. say: a = 1,2,3,4,5, b = 20,30,40,50,60 I want to get elements of a only when a = 3,4. I know I need indices but how ? Did you mean elements of b only where a = 3,4? b[(a==3) | (a==4)] -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion Ok, ok got it. Thanks Robert :) Following is what I have been looking for exactly. I[1]: a = arange(5) I[2]: b = arange(5)*10 I[3]: a O[3]: array([0, 1, 2, 3, 4]) I[4]: b O[4]: array([ 0, 10, 20, 30, 40]) I[5]: b[(a1) (a3)] O[5]: array([20]) I was forgetting the parenthesis, and consequently I was being bitten by ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() I am glad that it is not my understanding of logic but the usage of NumPy. -- Gökhan ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
