Re: [Numpy-discussion] median filtering a masked array
On 5 November 2014 19:11, Moroney, Catherine M (398E) catherine.m.moro...@jpl.nasa.gov wrote: What is the recommended way of doing a fast median filter on an array where only certain elements of the array need to be calculated? I'm trying to avoid a nested loop over all (I,J) elements. Since you are using FORTRAN, I believe the simplest way is to do this double loop in Cython. While you are at it, if you want to squeeze cycles, you can implement the median in Cython too. Here is some code: http://numpy-discussion.10968.n7.nabble.com/A-faster-median-Wirth-s-method-td14267.html /David. ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] median filtering a masked array
On 2014-11-06 11:10:29, Daπid davidmen...@gmail.com wrote: On 5 November 2014 19:11, Moroney, Catherine M (398E) catherine.m.moro...@jpl.nasa.gov wrote: What is the recommended way of doing a fast median filter on an array where only certain elements of the array need to be calculated? I'm trying to avoid a nested loop over all (I,J) elements. Since you are using FORTRAN, I believe the simplest way is to do this double loop in Cython. If you'd prefer to stay on the Python side, have a look at scipy.ndimage.generic_filter Stéfan ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
[Numpy-discussion] median filtering a masked array
Hello, I have to perform a median filter on only selected elements in an array and am wondering if using a masked array will speed things up by preventing the computation of the median on those elements where it's not needed. I'm using a Fortran code to fill up a (NX,NY,NZ) array where (NZ) is the number of points in the median filter window and NX and NY are the array dimensions themselves. If a filter is not required at a certain (I,J) element, I set all the elements along the NZ dimension to a fill value, and then create a masked array where the mask argument is set to True for all fill values. So, I am hoping that the numpy.median(data, axis=2) call will not even try to compute the median for those (I,J) elements where all the data in the NZ direction are masked out, thus saving me valuable computational time. Is this a valid assumption? Or does numpy go ahead and calculate the median for all (I,J) elements irregardless of whether they're masked out or not? What is the recommended way of doing a fast median filter on an array where only certain elements of the array need to be calculated? I'm trying to avoid a nested loop over all (I,J) elements. Catherine ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion