Re: [Numpy-discussion] getting indices for array positions
Hi Thanks for all your suggestions. Christian ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] getting indices for array positions
Christian Meesters uni-mainz.de> writes: > Since searchsorted returns the index of the first item in a that is >= or > > the key, it can't make the distinction between 0.1 and 0.2 as I would like to Then how about a.searchsorted(val+0.5) Christian ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] getting indices for array positions
On Wed, Feb 07, 2007 at 02:00:52PM +0100, Christian Meesters wrote: > This questions might seem stupid, but I didn't get a clever solution myself, > or found one in the archives, the cookbook, etc. . If I overlooked something, > please give a pointer. > > Well, if I have an 1D array like > [ 0. , 0.1, 0.2, 0.3, 0.4, 0.5] > ,a scalar like 0.122 and want to retrieve the index postion of the closest > value of the scalar in the array: Is there any fast method to get > this? If I understand correctly: data = N.array([ 0. , 0.1, 0.2, 0.3, 0.4, 0.5]) diff = N.abs(data - val) print N.argmin(diff) Regards Stéfan ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] getting indices for array positions
Christian Meesters wrote: >> Try searchsorted. > Thanks, but that doesn't work. Sorry, if my question wasn't clear. > > To illustrate the requirement: > For instance: a > array([ 0. , 0.1, 0.2, 0.3, 0.4]) # should be 1 > ... a.searchsorted(0.11) > 2 # should be 2 > ... a.searchsorted(0.16) > 2 > > I could correct for one index position, of course, but I still have the > requirement to get the index of the item with the closest value to the key. > Since searchsorted returns the index of the first item in a that is >= or > > the key, it can't make the distinction between 0.1 and 0.2 as I would like to > have. I see. But it gives you the index (say 'ii') of the first item that is grater than your scalar - then you just have to compare your scalar with a[ii] and a[ii-1] and choose whichever is closer, no? r. ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] getting indices for array positions
> Try searchsorted. Thanks, but that doesn't work. Sorry, if my question wasn't clear. To illustrate the requirement: For instance: >>> a array([ 0. , 0.1, 0.2, 0.3, 0.4]) >>> # should be 1 ... >>> a.searchsorted(0.11) 2 >>> # should be 2 ... >>> a.searchsorted(0.16) 2 I could correct for one index position, of course, but I still have the requirement to get the index of the item with the closest value to the key. Since searchsorted returns the index of the first item in a that is >= or > the key, it can't make the distinction between 0.1 and 0.2 as I would like to have. Hope this clarifies my question. Christian ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] getting indices for array positions
Christian Meesters wrote: > Hi > > This questions might seem stupid, but I didn't get a clever solution myself, > or found one in the archives, the cookbook, etc. . If I overlooked something, > please give a pointer. > > Well, if I have an 1D array like > [ 0. , 0.1, 0.2, 0.3, 0.4, 0.5] > ,a scalar like 0.122 and want to retrieve the index postion of the closest > value of the scalar in the array: Is there any fast method to get this? Try searchsorted. r. ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
[Numpy-discussion] getting indices for array positions
Hi This questions might seem stupid, but I didn't get a clever solution myself, or found one in the archives, the cookbook, etc. . If I overlooked something, please give a pointer. Well, if I have an 1D array like [ 0. , 0.1, 0.2, 0.3, 0.4, 0.5] ,a scalar like 0.122 and want to retrieve the index postion of the closest value of the scalar in the array: Is there any fast method to get this? Right now I've implemented the following method: def _get_value_index(value, a): mindiff = 1e20 index = 0 for intensity, temp_index in zip(a, xrange(a.shape[0])): diff = abs(intensity - value) #closer to given value? if diff <= mindiff: mindiff = diff index = temp_index return index It works, but is akward and takes too much time (I've no benchmark), if the array is long and the method called often within a different function. But it should help clarify the problem. TIA Christian ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
