Re: [Matplotlib-users] Basemap interp nearest neighbor
If I think of something, I'll let you know. In the meantime, I'd like to point out the following: Nearest neighbor returns a masked interpolation point if the nearest neighbor is masked (this is just what you've already told me). If there are two equidistant neighbors, it returns the one on the bottom. I, naively, expected it to return the unmasked one, but I suppose that this is just natural. It might be worth pointing this out in the documentation. Thanks again, Juan On 8/03/11 10:52 AM, Jeff Whitaker wrote: On 3/7/11 2:25 PM, Juan A. Saenz wrote: Jeff, thanks for your reply. One situation where one might require masked nearest neighbor interpolation is when, on a given fixed grid, interpolating velocities on cell corners (B-grid) to faces (C-grid). Cells will be defined as either land or ocean cells, masked or un-masked respectively. The masked or un-masked character of cells does not change. Interpolating velocities from corners adjacent to masked cells, to cell centers on un-masked cells will require the behavior in question. Imagine two adjacent cells, one masked and the other not. The velocities on the cell corners that lie on the coast (adjacent to a masked and an un-masked cell) are masked. A desireable behavior of the interpolator would be to produce an un-masked cell centered velocity on the un-masked cell that uses values from adjacent un-masked velocity values. Thanks, Juan Juan: I can see why you want it in this case, but I think in general users would expect a masked value if the nearest neighbor is masked. In addition, I don't see how to implement it easily. How far are you willing to go to find a nearest neighbor that is not masked? In short, for your use case you'll have to implement your own custom solution. Of course, if you can show me a simple modification to the Basemap interp function that does what you want, and can be enabled with a kwarg, I'll reconsider. -Jeff On 8/03/11 12:23 AM, Jeff Whitaker wrote: On 3/7/11 5:50 AM, Jeff Whitaker wrote: On 3/6/11 8:58 PM, Juan A. Saenz wrote: Hi, I use Basemap and netCDF4-python on a regular basis, and find them very useful tools. Thank you for developing them! I noticed that when using basemap.interp for nearest neighbor (order=0) the interpolation is not masked, and nearest neighbor masked values will be used in the interpolation. I was wondering if you could suggest a way to do nearest neighbor interpolation where masked are supported, i.e. nearest neighbor values that are not masked. Thanks for your help, Juan Juan: I agree that this would be desirable behavior. Unfortunately, it's not obvious to me how to do it. I'll think about it and get back to you. (cc'ing matplotlib-users list). -Jeff Juan: On second thought, I'm not sure this is desirable behavior. I would guess that most of the time, if a nearest neighbor is masked, the user would expect the interpolation routine to return a masked value. I would be interested to hear what others think. -Jeff -- Colocation vs. Managed Hosting A question and answer guide to determining the best fit for your organization - today and in the future. http://p.sf.net/sfu/internap-sfd2d ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] Basemap interp nearest neighbor
Jeff, thanks for your reply. One situation where one might require masked nearest neighbor interpolation is when, on a given fixed grid, interpolating velocities on cell corners (B-grid) to faces (C-grid). Cells will be defined as either land or ocean cells, masked or un-masked respectively. The masked or un-masked character of cells does not change. Interpolating velocities from corners adjacent to masked cells, to cell centers on un-masked cells will require the behavior in question. Imagine two adjacent cells, one masked and the other not. The velocities on the cell corners that lie on the coast (adjacent to a masked and an un-masked cell) are masked. A desireable behavior of the interpolator would be to produce an un-masked cell centered velocity on the un-masked cell that uses values from adjacent un-masked velocity values. Thanks, Juan On 8/03/11 12:23 AM, Jeff Whitaker wrote: On 3/7/11 5:50 AM, Jeff Whitaker wrote: On 3/6/11 8:58 PM, Juan A. Saenz wrote: Hi, I use Basemap and netCDF4-python on a regular basis, and find them very useful tools. Thank you for developing them! I noticed that when using basemap.interp for nearest neighbor (order=0) the interpolation is not masked, and nearest neighbor masked values will be used in the interpolation. I was wondering if you could suggest a way to do nearest neighbor interpolation where masked are supported, i.e. nearest neighbor values that are not masked. Thanks for your help, Juan Juan: I agree that this would be desirable behavior. Unfortunately, it's not obvious to me how to do it. I'll think about it and get back to you. (cc'ing matplotlib-users list). -Jeff Juan: On second thought, I'm not sure this is desirable behavior. I would guess that most of the time, if a nearest neighbor is masked, the user would expect the interpolation routine to return a masked value. I would be interested to hear what others think. -Jeff -- Juan A. Saenz Postdoctoral Fellow Geophysical Fluid Dynamics Research School of Earth Sciences Australian National University Building 61 Mills Road Canberra, ACT 0200 AUSTRALIA Office: +61 2 6125 9968 Admin: +61 2 6125 5502 Fax:+61 2 6257 2737 -- Colocation vs. Managed Hosting A question and answer guide to determining the best fit for your organization - today and in the future. http://p.sf.net/sfu/internap-sfd2d ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] Basemap interp nearest neighbor
On 3/6/11 8:58 PM, Juan A. Saenz wrote: Hi, I use Basemap and netCDF4-python on a regular basis, and find them very useful tools. Thank you for developing them! I noticed that when using basemap.interp for nearest neighbor (order=0) the interpolation is not masked, and nearest neighbor masked values will be used in the interpolation. I was wondering if you could suggest a way to do nearest neighbor interpolation where masked are supported, i.e. nearest neighbor values that are not masked. Thanks for your help, Juan Juan: I agree that this would be desirable behavior. Unfortunately, it's not obvious to me how to do it. I'll think about it and get back to you. (cc'ing matplotlib-users list). -Jeff -- What You Don't Know About Data Connectivity CAN Hurt You This paper provides an overview of data connectivity, details its effect on application quality, and explores various alternative solutions. http://p.sf.net/sfu/progress-d2d ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] Basemap interp nearest neighbor
On 3/7/11 5:50 AM, Jeff Whitaker wrote: On 3/6/11 8:58 PM, Juan A. Saenz wrote: Hi, I use Basemap and netCDF4-python on a regular basis, and find them very useful tools. Thank you for developing them! I noticed that when using basemap.interp for nearest neighbor (order=0) the interpolation is not masked, and nearest neighbor masked values will be used in the interpolation. I was wondering if you could suggest a way to do nearest neighbor interpolation where masked are supported, i.e. nearest neighbor values that are not masked. Thanks for your help, Juan Juan: I agree that this would be desirable behavior. Unfortunately, it's not obvious to me how to do it. I'll think about it and get back to you. (cc'ing matplotlib-users list). -Jeff Juan: On second thought, I'm not sure this is desirable behavior. I would guess that most of the time, if a nearest neighbor is masked, the user would expect the interpolation routine to return a masked value. I would be interested to hear what others think. -Jeff -- What You Don't Know About Data Connectivity CAN Hurt You This paper provides an overview of data connectivity, details its effect on application quality, and explores various alternative solutions. http://p.sf.net/sfu/progress-d2d ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] Basemap interp nearest neighbor
On a similar note, are there any alternatives available to nearest neighbor? For example, kriging? I remember seeing a geostats library in python (hpgl i think), but I found the API rather impractical and difficult to use. Thanks, Aman On Mon, Mar 7, 2011 at 8:23 AM, Jeff Whitaker jsw...@fastmail.fm wrote: On 3/7/11 5:50 AM, Jeff Whitaker wrote: On 3/6/11 8:58 PM, Juan A. Saenz wrote: Hi, I use Basemap and netCDF4-python on a regular basis, and find them very useful tools. Thank you for developing them! I noticed that when using basemap.interp for nearest neighbor (order=0) the interpolation is not masked, and nearest neighbor masked values will be used in the interpolation. I was wondering if you could suggest a way to do nearest neighbor interpolation where masked are supported, i.e. nearest neighbor values that are not masked. Thanks for your help, Juan Juan: I agree that this would be desirable behavior. Unfortunately, it's not obvious to me how to do it. I'll think about it and get back to you. (cc'ing matplotlib-users list). -Jeff Juan: On second thought, I'm not sure this is desirable behavior. I would guess that most of the time, if a nearest neighbor is masked, the user would expect the interpolation routine to return a masked value. I would be interested to hear what others think. -Jeff -- What You Don't Know About Data Connectivity CAN Hurt You This paper provides an overview of data connectivity, details its effect on application quality, and explores various alternative solutions. http://p.sf.net/sfu/progress-d2d ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users -- What You Don't Know About Data Connectivity CAN Hurt You This paper provides an overview of data connectivity, details its effect on application quality, and explores various alternative solutions. http://p.sf.net/sfu/progress-d2d___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] Basemap interp nearest neighbor
On 3/7/11 7:38 AM, Aman Thakral wrote: On a similar note, are there any alternatives available to nearest neighbor? For example, kriging? I remember seeing a geostats library in python (hpgl i think), but I found the API rather impractical and difficult to use. Thanks, Aman Aman: The basemap interp function is just a convenience function for simple regridding (linear, cubic and nearest neighbor). scipy.interpolate (http://docs.scipy.org/doc/scipy/reference/interpolate.html) provides many more options. -Jeff On Mon, Mar 7, 2011 at 8:23 AM, Jeff Whitaker jsw...@fastmail.fm mailto:jsw...@fastmail.fm wrote: On 3/7/11 5:50 AM, Jeff Whitaker wrote: On 3/6/11 8:58 PM, Juan A. Saenz wrote: Hi, I use Basemap and netCDF4-python on a regular basis, and find them very useful tools. Thank you for developing them! I noticed that when using basemap.interp for nearest neighbor (order=0) the interpolation is not masked, and nearest neighbor masked values will be used in the interpolation. I was wondering if you could suggest a way to do nearest neighbor interpolation where masked are supported, i.e. nearest neighbor values that are not masked. Thanks for your help, Juan Juan: I agree that this would be desirable behavior. Unfortunately, it's not obvious to me how to do it. I'll think about it and get back to you. (cc'ing matplotlib-users list). -Jeff Juan: On second thought, I'm not sure this is desirable behavior. I would guess that most of the time, if a nearest neighbor is masked, the user would expect the interpolation routine to return a masked value. I would be interested to hear what others think. -Jeff -- What You Don't Know About Data Connectivity CAN Hurt You This paper provides an overview of data connectivity, details its effect on application quality, and explores various alternative solutions. http://p.sf.net/sfu/progress-d2d ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net mailto:Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users -- What You Don't Know About Data Connectivity CAN Hurt You This paper provides an overview of data connectivity, details its effect on application quality, and explores various alternative solutions. http://p.sf.net/sfu/progress-d2d___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] Basemap interp nearest neighbor
On 3/7/11 2:25 PM, Juan A. Saenz wrote: Jeff, thanks for your reply. One situation where one might require masked nearest neighbor interpolation is when, on a given fixed grid, interpolating velocities on cell corners (B-grid) to faces (C-grid). Cells will be defined as either land or ocean cells, masked or un-masked respectively. The masked or un-masked character of cells does not change. Interpolating velocities from corners adjacent to masked cells, to cell centers on un-masked cells will require the behavior in question. Imagine two adjacent cells, one masked and the other not. The velocities on the cell corners that lie on the coast (adjacent to a masked and an un-masked cell) are masked. A desireable behavior of the interpolator would be to produce an un-masked cell centered velocity on the un-masked cell that uses values from adjacent un-masked velocity values. Thanks, Juan Juan: I can see why you want it in this case, but I think in general users would expect a masked value if the nearest neighbor is masked. In addition, I don't see how to implement it easily. How far are you willing to go to find a nearest neighbor that is not masked? In short, for your use case you'll have to implement your own custom solution. Of course, if you can show me a simple modification to the Basemap interp function that does what you want, and can be enabled with a kwarg, I'll reconsider. -Jeff On 8/03/11 12:23 AM, Jeff Whitaker wrote: On 3/7/11 5:50 AM, Jeff Whitaker wrote: On 3/6/11 8:58 PM, Juan A. Saenz wrote: Hi, I use Basemap and netCDF4-python on a regular basis, and find them very useful tools. Thank you for developing them! I noticed that when using basemap.interp for nearest neighbor (order=0) the interpolation is not masked, and nearest neighbor masked values will be used in the interpolation. I was wondering if you could suggest a way to do nearest neighbor interpolation where masked are supported, i.e. nearest neighbor values that are not masked. Thanks for your help, Juan Juan: I agree that this would be desirable behavior. Unfortunately, it's not obvious to me how to do it. I'll think about it and get back to you. (cc'ing matplotlib-users list). -Jeff Juan: On second thought, I'm not sure this is desirable behavior. I would guess that most of the time, if a nearest neighbor is masked, the user would expect the interpolation routine to return a masked value. I would be interested to hear what others think. -Jeff -- Jeffrey S. Whitaker Phone : (303)497-6313 Meteorologist FAX: (303)497-6449 NOAA/OAR/PSD R/PSD1Email : jeffrey.s.whita...@noaa.gov 325 BroadwayOffice : Skaggs Research Cntr 1D-113 Boulder, CO, USA 80303-3328 Web: http://tinyurl.com/5telg -- What You Don't Know About Data Connectivity CAN Hurt You This paper provides an overview of data connectivity, details its effect on application quality, and explores various alternative solutions. http://p.sf.net/sfu/progress-d2d ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] Basemap interp
Andrew, I sent this to you personally, unintentionally, and want it to be on the list too. So you have it doubled now, sorry. 2010/2/25 Andrew Charles ac1...@gmail.com: I'm trying to interpolate from one grid to another using Basemap's interp function. It seems to want the lat and lon axis of the new grid to have the same shape: 3524 if xout.shape != yout.shape: 3535 raise ValueError, 'xout and yout must have same shape!' The grid I'm interpolating to is 144 by 72 I'm calling it as interp(x,lon,lat,plon,plat) where lon and plon are numpy arrays with shape (144,) lat has shape (73,) plat has shape(72,) and x has shape (72, 144) Does interp() really only work if the target grid is square? I guess it wants a meshgrid, use e.g.: lats = len(lat) lons = len(lon) lat = lat[:, numpy.newaxis].repeat(lons, axis = 1) lon = lon[numpy.newaxis, :].repeat(lats, axis = 0) - or the other way round - lat = lat[numpy.newaxis, :].repeat(lons, axis = 0) lon = lat[:, numpy.newaxis].repeat(lats, axis = 1) depending on what axis lat and lon should respectively be associated with. A meshgrid is a sequence of coordinate grids. For each point KEY, the coordinates are MESHGRID[:, KEY]. Thus you can via meshgrids specifiy also distorted grids to interpolate to (e.g. a wavy rectangular grid or something). (I guess this is actually needed when doing Mercator to Postels or similar). Friedrich -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] Basemap interp
On Thu, Feb 25, 2010 at 7:26 PM, Friedrich Romstedt friedrichromst...@gmail.com wrote: 2010/2/25 Andrew Charles ac1...@gmail.com: I'm trying to interpolate from one grid to another using Basemap's interp function. It seems to want the lat and lon axis of the new grid to have the same shape: 3524 if xout.shape != yout.shape: 3535 raise ValueError, 'xout and yout must have same shape!' The grid I'm interpolating to is 144 by 72 I'm calling it as interp(x,lon,lat,plon,plat) where lon and plon are numpy arrays with shape (144,) lat has shape (73,) plat has shape(72,) and x has shape (72, 144) Does interp() really only work if the target grid is square? I guess it wants a meshgrid Aye, now that I read the docstring with a rested pair of eyes it's clear that xout and yout are meshgrids (rank 2 arrays). Thanks, problem solved. - Andrew Charles -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] Basemap interp
2010/2/26 Andrew Charles ac1...@gmail.com: Aye, now that I read the docstring with a rested pair of eyes it's clear that xout and yout are meshgrids (rank 2 arrays). Thanks, problem solved. For convenience, I recently heard about numpy.meshgrid, which does the job for you. See its __doc__, but it's fairly easy: numpy.meshgrid(x, y). Friedrich -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
[Matplotlib-users] Basemap interp
I'm trying to interpolate from one grid to another using Basemap's interp function. It seems to want the lat and lon axis of the new grid to have the same shape: 3524 if xout.shape != yout.shape: 3535 raise ValueError, 'xout and yout must have same shape!' The grid I'm interpolating to is 144 by 72 I'm calling it as interp(x,lon,lat,plon,plat) where lon and plon are numpy arrays with shape (144,) lat has shape (73,) plat has shape(72,) and x has shape (72, 144) Does interp() really only work if the target grid is square? - Andrew Charles -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
