1.4 Modifying & filtering detection data
Both the Detections and DetectionsList objects have a number of generics which facilitate the handling of data.
subset can be applied to both Detections and DetectionsList objects.
# Filter PPM tags after 8:00 PM
detlst_sub <- subset(exdata_positioning,
second >= as.POSIXct("2021-05-08 20:00:00", tz = "CET") & type %in% c("PPM", "PPM_SELF"))
detlst_sub## DetectionsList
##
## Receiver Summary
## 1 2 3 4 5 6
## Sync-tag ID 62041 62042 62074 62368 62581 62584
## Sync-tag emissions 119 120 119 120 118 119
## Tag detections 476 482 458 442 445 349
## Tags detected 6 6 6 6 6 5
##
## Detections Summary
## Tag-ID First detection Last detection n Detection period (h)
## 62074 2021-05-08 20:04:05 2021-05-09 05:59:56 476 9.93
## 62368 2021-05-08 20:01:15 2021-05-09 05:55:31 457 9.90
## 62584 2021-05-08 20:02:09 2021-05-09 05:52:23 439 9.84
## 62042 2021-05-08 20:03:05 2021-05-09 05:56:37 414 9.89
## 62041 2021-05-08 20:04:15 2021-05-09 05:58:01 414 9.90
## 62581 2021-05-08 20:02:41 2021-05-09 05:55:42 380 9.88
## PPM-53883 2021-05-08 20:55:51 2021-05-08 21:22:06 72 0.44For Detections objects, we can easily subset rows with indexing.
## Telemetry Detections
## Name: 1
## Sync-tag ID: 62041
## Depth: NA
## Coords: (481460.3 m, 6243492 m)
## Sync tag emissions: 1
## Detections: 5
## First detection on: 2021-05-08 18:00:09
## Last detection on: 2021-05-08 18:05:23
## Time zone: CET
## second millisecond detect_id type sync_emission
## 1 2021-05-08 18:00:09 427.3985 62074 PPM FALSE
## 2 2021-05-08 18:00:38 772.6640 62042 PPM FALSE
## 3 2021-05-08 18:00:48 244.0411 62584 PPM FALSE
## 4 2021-05-08 18:01:03 878.7920 PPM_SELF PPM_SELF TRUE
## 5 2021-05-08 18:02:21 749.5333 62368 PPM FALSE
## 6 2021-05-08 18:05:23 948.8101 62074 PPM FALSEWe can also apply offsets to the clock values.
# Subtract 10.5 seconds from the first 3 detection times
det_1[1:3] <- det_1[1:3] - 10.5
head(det_1)## Telemetry Detections
## Name: 1
## Sync-tag ID: 62041
## Depth: NA
## Coords: (481460.3 m, 6243492 m)
## Sync tag emissions: 1
## Detections: 5
## First detection on: 2021-05-08 17:59:58
## Last detection on: 2021-05-08 18:05:23
## Time zone: CET
## second millisecond detect_id type sync_emission
## 1 2021-05-08 17:59:58 927.3985 62074 PPM FALSE
## 2 2021-05-08 18:00:28 272.6640 62042 PPM FALSE
## 3 2021-05-08 18:00:37 744.0411 62584 PPM FALSE
## 4 2021-05-08 18:01:03 878.7920 PPM_SELF PPM_SELF TRUE
## 5 2021-05-08 18:02:21 749.5333 62368 PPM FALSE
## 6 2021-05-08 18:05:23 948.8101 62074 PPM FALSE