| MPFIT2DFUN- use for a time series of images? [message #75507] |
Thu, 10 March 2011 12:01  |
![Katie[1] is currently offline](theme/default/images/xoffline.png.pagespeed.ic.XRkd1fkXye.png "Katie[1] is currently offline")
Katie[1]
Messages: 2
Registered: March 2011
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Junior Member |
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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)?
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| Re: MPFIT2DFUN- use for a time series of images? [message #87551 is a reply to message #75507] |
Fri, 14 February 2014 11:47  |
rajen.water
Messages: 1
Registered: February 2014
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Junior Member |
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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
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| 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
>
>> 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
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