comp.lang.idl-pvwave archive - RDF feed
type: channel
description: Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
items: Re: Surface fitting image with missing data

Re: Surface fitting image with missing data
type: item
description: On 31 Jul., 02:12, jradavenp...@gmail.com wrote: > Hey all; > > I have a 2-D array (essentially an image) with dimensions [n,m] > > There is a large chunk in a corner of the image with no data. All > pixels have values greater than 1, except within this chunk, which = > 0. > > SFIT fits these as valid points and tips my surface (a plane) towards > this corner! I thought I would be terribly clever by doing the > following: > > result = sfit( finite(image/(image gt 0)),1,/max_degree) > > alas, SFIT isnt playing ball and makes a whole array of /NaN... > > Thoughts? Is there a version of SFIT (or something similar) with a / > NaN keyword? A more clever way to fit a simple surface to an image > with missing data? Thanks folks > > - Jim Hello Jim I can highly recommend the library from Craig Markwardt. I use mpfitfun for 2D fitting. Among one of the many useful features is the ability to do curvefit on data points set to NaN!!!! http://cow.physics.wisc.edu/~craigm/idl/idl.html Cheers Werner
creator: werner.hupfer
date: 2008-07-31T08:27:33-00:00

Re: Surface fitting image with missing data
type: item
description: werner.hupfer@googlemail.com writes: > On 31 Jul., 02:12, jradavenp...@gmail.com wrote: >> Hey all; >> >> I have a 2-D array (essentially an image) with dimensions [n,m] >> >> There is a large chunk in a corner of the image with no data. All >> pixels have values greater than 1, except within this chunk, which = >> 0. ... > > I can highly recommend the library from Craig Markwardt. I use > mpfitfun for 2D fitting. Among one of the many useful features is the > ability to do curvefit on data points set to NaN!!!! > > http://cow.physics.wisc.edu/~craigm/idl/idl.html Thanks for the plug! Actually MPFIT doesn't accept NaNs but probably should. Even so, you can set the WEIGHTS to zero for your missing data (or equivalently, the ERRORs to a very large number). Craig -- ------------------------------------------------------------ -------------- Craig B. Markwardt, Ph.D. EMAIL: craigmnet@REMOVEcow.physics.wisc.edu Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response ------------------------------------------------------------ --------------
creator: Craig Markwardt
date: 2008-08-04T04:52:20-00:00