"lastIndependentRecord" and "lastRecord" difference in "deltaTimeComparedTo" for recordtable

[Camilo Benitez R]

I'm new working with camptrapR and currently trying to figure out the difference between "lastIndependentRecord" and  "lastRecord" diference in deltaTimeComparedTo" in order to create my recordtable. I read the vignettes, the pdf, and other related materials but still not fully understand the difference. I think that and example can help a lot. I know this could be a silly question but it is really important to begin data analysis. Please can someone explain what this means, my attempts to find out through a web search has so far failed.

Kind regards

Camilo

[Juergen Niedballa]

Hi Camilo,

I don't have example data at hand, but imagine this scenario:

A species is detected at a station 3 times in the same day:  1:00pm, 1:30pm, 2:10pm

You run recordTable() with minDeltaTime = 60. The first record (1:00 pm) will always be returned. deltaTimeComparedTo controls how the time differences of the remaining records (record 2 and 3 in this example) are calculated and which of these are returned.

deltaTimeComparedTo = "lastIndependentRecord" 

• Record 1: is considered an independent record and will be returned
• Record 2: time difference to last independent record (record 1) = 30 minutes. Record 2 is therefore not independent and will be omitted (time difference to last independent record < 60 minutes).
• Record 3: time difference to last independent record (record 1) = 70 minutes. Record 3 is therefore independent and will be returned (time difference to last independent record > 60 minutes).

> recordTable returns record 1 and 3

deltaTimeComparedTo = "lastRecord"

• Record 1: is considered an independent record and will be returned
• Record 2: time difference to last record (record 1) = 30 minutes. Record 2 is therefore not independent and will be omitted (time difference to last record < 60 minutes).
• Record 3: time difference to last record (record 2) = 40 minutes. Record 3 is therefore not independent and will be omitted (time difference to last record < 60 minutes).

> recordTable returns only record 1

In a more extreme example, imagine records of a species every 10 minutes. minDeltaTime is still 60 minutes.

deltaTimeComparedTo = "lastIndependentRecord" will return the first record and then records every hour.

deltaTimeComparedTo = "lastRecord" will only return the first record, since all subsequent time intervals are less than 60 minutes.

If minDeltaTime = 0, how you set deltaTimeComparedTo doesn't make a difference.

Hope this helps understand how the argument works. If you have further questions, please feel free to ask. I will also add a more in-depth explanation in the vignettes. Thank you for the suggestion.

Best regards,

Jürgen