diff --git a/.gitignore b/.gitignore
index 57ce24b..6f3bfb3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,5 +17,7 @@ __pycache__/
 /presentation/*scores.csv
 /presentation/Results.ods
 .Rproj.user
+.Rhistory
 /presentation/*.nb.html
-/presentation/
+presentation/event_stressful_detection_half_loso.csv
+presentation/event_stressful_detection_loso.csv
diff --git a/presentation/ApplicationCategories.R b/presentation/ApplicationCategories.R
new file mode 100644
index 0000000..f229ac5
--- /dev/null
+++ b/presentation/ApplicationCategories.R
@@ -0,0 +1,51 @@
+library(conflicted)
+library(yaml)
+library(RPostgreSQL)
+library(tidyverse)
+conflicts_prefer(
+  dplyr::filter,
+  dplyr::lag
+)
+library(magrittr)
+
+# read the password from file
+credentials <- yaml.load_file("../rapids/credentials.yaml")
+pw <- credentials$PSQL_STRAW$password
+
+# load the PostgreSQL driver
+drv <- RPostgres::Postgres()
+
+# creates a connection to the postgres database
+# note that "con" will be used later in each connection to the database
+con <- RPostgres::dbConnect(drv,
+  dbname = "staw",
+  host = "eol.ijs.si", port = 5432,
+  user = "staw_db", password = pw
+)
+
+rm(pw, credentials) # removes the password
+
+# check for the bluetooth table, an example
+dbExistsTable(con, "app_categories")
+
+df_app_categories <- tbl(con, "app_categories") %>%
+  collect()
+
+head(df_app_categories)
+table(df_app_categories$play_store_genre)
+
+# Correct some mistakes
+df_app_categories %<>% mutate(
+  play_store_genre = {
+    function(x) {
+      case_when(
+        x == "Education,Education" ~ "Education",
+        x == "EducationEducation" ~ "Education",
+        x == "not_found" ~ "System",
+        .default = x
+      )
+    }
+  }(play_store_genre)
+)
+
+dbDisconnect(con)