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Error when setting twilight threshold

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I'm working on my thesis playing with the GCSP tag data sets, trying to process them with GeoLocTools and FLightR. I am coming up on an error message when I selecting my twilight threshold. I have tried changing the threshold a variety of different times and still receive the same error message.

> threshold <- 0.6

> twl <- preprocessLight(raw, 
+   threshold = threshold,
+   offset = offset, 
+   lmax = 20, # max. light value (adjust if contrast between night and day is weak)
+   gr.Device = "x11") 
Waiting for input
Error in class(xx) <- cl : attempt to set an attribute on NULL

Any thoughts or suggestion would be greatly appreciated. 

Thank you so much

Diane Nelson

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Hi Diane, have you plotted your light data to make sure that the threshold is within the range of measured light. And have you got any NA's in your time column (check for sum(is.na(raw$Date))).


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Hi Simeon,

Thank you so much for responding. I checked my NA's and didn't get any. 

      Date                         Light        
 Min.   :2013-02-22 00:00:02   Min.   : 0.0002  
 1st Qu.:2013-04-28 17:58:47   1st Qu.: 0.0002  
 Median :2013-07-03 11:57:32   Median : 6.4847  
 Mean   :2013-07-03 11:57:32   Mean   : 5.1559  
 3rd Qu.:2013-09-07 05:56:17   3rd Qu.: 8.8506  
 Max.   :2013-11-11 23:55:02   Max.   :11.2176


I set the threshold to -.6, .6, 1, 2. I went through the steps to select the beginning, ending date and the darkest spot in the no light area in order for the package to select the sunrise and sunsets. I accepted all the other screens and then the error keeps happening particularly when I hit  (a)accept for stage depicted in the attached image. 


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