| Re: MPFIT2DFUN- use for a time series of images? [message #87561 is a reply to message #87551] |
Fri, 14 February 2014 21:56  |
Craig Markwardt
Messages: 1869
Registered: November 1996
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Senior Member |
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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
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>> coordinates and a day of the year value associated with them. I see
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>> from the MPFIT2DFUN documentation how to define X, Y for a each Z
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>> dependent value and the dependent error value, but can a third
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>> variable (day of the year in this case) be defined in order to fit a
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>> curve in MPFIT2DFUN? I currently have each each date as a separate
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>> band in a stacked image file that I exported as an ASCII file. I want
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>> to determine the day of the year that the pixel values (vegetation
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>> indices) reach a value on the the curve.
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> 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
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