Lab 3: Fixes for assignment 2, according to seminar

lab3/assignment2.R

@@ -32,7 +32,7 @@ times <- c(
 st$time <- strptime(st$time, format = "%H:%M:%S")
 
 gaussian_kernel <- function(x, h) {
-  exp(-(x ^ 2) / (2 * h ^ 2))
+  exp(-(x^2) / (2 * h^2))
 }
 
 x = seq(0, 300000, length.out = 1000)
@@ -66,7 +66,6 @@ plot(
 grid()
 
 date_diff_ignoring_year <- function(date1, date2) {
-  
   # Generate new dates with the same year
   date1 <- strsplit(date1, "-")[[1]]
   date2 <- strsplit(date2, "-")[[1]]
@@ -78,10 +77,22 @@ date_diff_ignoring_year <- function(date1, date2) {
   date2 <- as.Date(paste("2000", month2, day2, sep = "-"))
   
   # Get difference in days
-  diff <- abs(as.numeric(date1-date2))
-
+  diff <- abs(as.numeric(date1 - date2))
+  
   # If difference is greater than half a year, go other way
-  if (diff >= 183) diff <- 366 - diff
+  if (diff >= 183)
+    diff <- 366 - diff
+  
+  return(diff)
+}
+
+difftime_ignoring_day <- function(time1, time2) {
+  # Get difference in hours
+  diff <- abs(as.numeric(difftime(time1, time2, units = "hours")))
+  
+  # If difference is grater than 12 hours, go other way
+  if (diff > 12)
+    diff <- abs(diff - 24)
   
   return(diff)
 }
@@ -96,8 +107,9 @@ for (time in times) {
   # Filter out posterior dates and time
   st_temp <- st[st$date < date |
                   (st$date == date &
-                     st$time <= time), ]
+                     st$time < time), ]
   
+  # Normalize data?
   
   distance_kernels <- mapply(function(lat, lon) {
     dist <- distHaversine(c(a, b), c(lat, lon))
@@ -112,7 +124,7 @@ for (time in times) {
   
   
   time_kernels <- mapply(function(time_i) {
-    dist <- as.numeric(difftime(time, time_i, units = "hours"))
+    dist <- difftime_ignoring_day(time, time_i)
     gaussian_kernel(dist, h_time)
   }, st_temp$time)