Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
MPFIT2DFUN- use for a time series of images?
I want to fit pixel values to a logistic model that each have X, Y coordinates and a day of the year value associated with them. I see from the MPFIT2DFUN documentation how to define X, Y for a each Z dependent value and the dependent error value, but can a third variable (day of the year in this case) be defined in order to fit a curve in MPFIT2DFUN? I currently have each each date as a separate band in a stacked image file that I exported as an ASCII file. I want to determine the day of the year that the pixel values (vegetation indices) reach a value on the the curve. Any suggestions, or perhaps I am not understanding the MPFIT2DFUN correctly (I am very new to IDL)?
Re: MPFIT2DFUN- use for a time series of images?
On Thursday, March 10, 2011 3:01:14 PM UTC-5, Katie wrote: > I want to fit pixel values to a logistic model that each have X, Y > coordinates and a day of the year value associated with them. I see > from the MPFIT2DFUN documentation how to define X, Y for a each Z > dependent value and the dependent error value, but can a third > variable (day of the year in this case) be defined in order to fit a > curve in MPFIT2DFUN? I currently have each each date as a separate > band in a stacked image file that I exported as an ASCII file. I want > to determine the day of the year that the pixel values (vegetation > indices) reach a value on the the curve. > > Any suggestions, or perhaps I am not understanding the MPFIT2DFUN > correctly (I am very new to IDL)? Hi Katie, Were you able to solve your problem? I do have the similar problem now. Best, Rajendra
On Friday, February 14, 2014 2:47:33 PM UTC-5, rajen...@gmail.com wrote: > On Thursday, March 10, 2011 3:01:14 PM UTC-5, Katie wrote: > >> I want to fit pixel values to a logistic model that each have X, Y > >> coordinates and a day of the year value associated with them. I see > >> from the MPFIT2DFUN documentation how to define X, Y for a each Z > >> dependent value and the dependent error value, but can a third > >> variable (day of the year in this case) be defined in order to fit a > >> curve in MPFIT2DFUN? I currently have each each date as a separate > >> band in a stacked image file that I exported as an ASCII file. I want > >> to determine the day of the year that the pixel values (vegetation > >> indices) reach a value on the the curve. > > Were you able to solve your problem? I do have the similar problem now. The easiest way to solve Katie's problem is to use the FUNCTARGS option. For example, if DOY is day of year, pp = mpfit2dfun(myfunct, x, y, z, err, pp0, functargs={doy: doy}) and then MYFUNCT needs to accept the DOY keyword, function myfunct, x, y, p, doy=doy ;; calculate function based on x, y and doy return, f end Another way is described here, http://www.physics.wisc.edu/~craigm/idl/fitqa.html#multivar Basically MPFIT doesn't care how many independent your function has. That is ancillary information that only you need to know. All you need to do is find a way to get that data into your user function. Craig