Fix screen delta extraction for iOS and Android

rules/features.snakefile

@@ -32,7 +32,8 @@ rule battery_deltas:
 
 rule screen_deltas:
     input:
-        "data/raw/{pid}/screen_with_datetime.csv"
+        screen = "data/raw/{pid}/screen_with_datetime.csv",
+        participant_info = "data/external/{pid}"
     output:
         "data/processed/{pid}/screen_deltas.csv"
     script:

src/features/screen_deltas.R

@@ -1,37 +1,81 @@
 source("packrat/init.R")
 
-library("tidyverse")
+library(dplyr)
+library(tidyr)
+library(stringr)
 
-screen <- read.csv(snakemake@input[[1]])
+screen <- read.csv(snakemake@input[["screen"]])
+participant_info <- snakemake@input[["participant_info"]]
+platform <- readLines(participant_info, n=2)[[2]]
 
-if(nrow(screen) > 0){
+# Screen States
-  unlock_episodes <-
+# Android: https://github.com/denzilferreira/aware-client/blob/78ccc22f0f822f8421bef9b1a73d36e71b8aa85b/aware-core/src/main/java/com/aware/Screen.java
-    screen %>%
+# iOS: https://github.com/tetujin/aware-client-ios-v2/blob/master/Pods/AWAREFramework/AWAREFramework/Classes/Sensors/Screen/Screen.m#L120
-    # in iOS there are unlock (3) events on the same second, discard them
+# 0. OFF (Not existent for iOS due to API limitations)
-    distinct(screen_status, utc_date_time, .keep_all = TRUE) %>%
+# 1. ON (Not existent for iOS due to API limitations)
-    # in Android we discard on and off events (0,1) for now (iOS does not collect them)
+# 2. LOCKED
-    filter(screen_status == 2 | screen_status == 3) %>% 
+# 3. UNLOCKED
-    # create groups of consecutive unlock/lock (3/2) events
+
-    mutate(screen_episode = cumsum(c(1, head(screen_status, -1) == 2 & tail(screen_status, -1) == 3))) %>% 
+swap_screen_status <- function(data, status1, status2, time_buffer){
-    group_by(screen_episode) %>%
+  # 800L is an auxiliary state to swap
-    # in Android there are multiple consecutive unlock/lock events so we keep the closest pair
+  data %>% mutate(screen_status = case_when(screen_status == status2 & lag(screen_status) == status1 & (timestamp - lag(timestamp)) < time_buffer ~ 800L,
-    # this happens because ACTION_SCREEN_OFF and ON are "sent when the device becomes non-interactive 
+                                            TRUE ~ screen_status),
-    # which may have nothing to do with the screen turning off" see:
+                  screen_status = case_when(screen_status == status1 & lead(screen_status) == 800L ~ status2,
-    # https://developer.android.com/reference/android/content/Intent.html#ACTION_SCREEN_OFF
+                                            TRUE ~ screen_status),
-    filter((screen_status == 2 & screen_status != lag(screen_status, default="1")) |
+                  screen_status = ifelse(screen_status == 800L, status1, screen_status))
-            (screen_status == 3 & screen_status != lead(screen_status, default="1"))) %>%
+}
-    filter(n() == 2) %>%
+
-    summarize(episode = "unlock",
+get_ios_screen_episodes <- function(screen){
-              time_diff = (last(timestamp) - first(timestamp)) / (1000 * 60),
+  episodes <- screen %>%
+    # only keep consecutive pairs of 3,2 events
+    filter( (screen_status == 3 & lead(screen_status) == 2) | (screen_status == 2 & lag(screen_status) == 3) ) %>%
+    # in iOS and after our filtering, screen episodes should end with a LOCK event (2)
+    mutate(episode_id = ifelse(screen_status == 2, 1:n(), NA_integer_)) %>%
+    fill(episode_id, .direction = "updown") %>%
+    group_by(episode_id) %>%
+    summarise(episode = "unlock",
+              screen_sequence = toString(screen_status),
+              time_diff = (last(timestamp) - first(timestamp)) / 1000,
+              local_start_date_time = first(local_date_time),
+              local_end_date_time = last(local_date_time),
+              local_start_date = first(local_date),
+              local_end_date = last(local_date),
+              local_start_day_segment = first(local_day_segment),
+              local_end_day_segment = last(local_day_segment))
+}
+
+get_android_screen_episodes <- function(screen){
+  episodes <- screen %>% 
+    # filter out UNLOCK events (2) that come within 50 milliseconds of an ON or OFF event
+    filter(!(screen_status == 2 & lag(screen_status) == 1 & timestamp - lag(timestamp) < 50)) %>% 
+    filter(!(screen_status == 2 & lag(screen_status) == 0 & timestamp - lag(timestamp) < 50)) %>% 
+    # in Android and after our filtering, screen episodes should end with a OFF event (0)
+    mutate(episode_id = ifelse(screen_status == 0, 1:n(), NA_integer_)) %>% 
+    fill(episode_id, .direction = "updown") %>% 
+    group_by(episode_id)  %>% 
+    # Rarely, UNLOCK events (3) get logged just before ON events (1). If this happens within 800ms, swap them
+    swap_screen_status(3L, 1L, 800) %>% 
+    # to be consistent with iOS we get rid off events (and thus sequences) starting with an ON (1) event
+    filter(screen_status != 1) %>%
+    summarise(episode = "unlock",
+              screen_sequence = toString(screen_status),
+              time_diff = (last(timestamp) - first(timestamp)) / 1000,
               local_start_date_time = first(local_date_time),
               local_end_date_time = last(local_date_time),
               local_start_date = first(local_date),
               local_end_date = last(local_date),
               local_start_day_segment = first(local_day_segment),
               local_end_day_segment = last(local_day_segment)) %>% 
-    select(-screen_episode)
+    filter(str_detect(screen_sequence,
-} else {
+                      paste0("^(",
-  unlock_episodes <- data.frame(episode = character(), 
+                            paste(c(3), collapse = "|"), # Filter sequences that start with 3 (UNLOCK) AND
+                            ").*(",
+                            paste(c(0), collapse = "|"), # Filter sequences that end with 0 (OFF)
+                            ")$")))
+}
+
+if(nrow(screen) < 1){
+  episodes <- data.frame(episode = character(), 
                                 time_diff = numeric(),
                                 local_start_date_time = character(),
                                 local_end_date_time = character(),
@@ -39,6 +83,12 @@ if(nrow(screen) > 0){
                                 local_end_date = character(),
                                 local_start_day_segment = character(),
                                 local_end_day_segment = character())
+} else if(platform == "ios"){
+  episodes <- get_ios_screen_episodes(screen)
+} else if(platform == "android"){
+  episodes <- get_android_screen_episodes(screen)
+} else {
+  print(paste0("The platform (second line) in ", participant_info, " should be android or ios"))
 }
 
-write.csv(unlock_episodes, snakemake@output[[1]], row.names = FALSE)
+write.csv(episodes, snakemake@output[[1]], row.names = FALSE)