Data commit

Task/Ray-casting-algorithm/R/ray-casting-algorithm-1.r

@@ -0,0 +1,44 @@
+point_in_polygon <- function(polygon, p) {
+  count <- 0
+  for(side in polygon) {
+    if ( ray_intersect_segment(p, side) ) {
+      count <- count + 1
+    }
+  }
+  if ( count %% 2 == 1 )
+    "INSIDE"
+  else
+    "OUTSIDE"
+}
+
+ray_intersect_segment <- function(p, side) {
+  eps <- 0.0001
+  a <- side$A
+  b <- side$B
+  if ( a$y > b$y ) {
+    a <- side$B
+    b <- side$A
+  }
+  if ( (p$y == a$y) || (p$y == b$y) ) {
+    p$y <- p$y + eps
+  }
+  if ( (p$y < a$y) || (p$y > b$y) )
+    return(FALSE)
+  else if ( p$x > max(a$x, b$x) )
+    return(FALSE)
+  else {
+    if ( p$x < min(a$x, b$x) )
+      return(TRUE)
+    else {
+      if ( a$x != b$x )
+        m_red <- (b$y - a$y) / (b$x - a$x)
+      else
+        m_red <- Inf
+      if ( a$x != p$x )
+        m_blue <- (p$y - a$y) / (p$x - a$x)
+      else
+        m_blue <- Inf
+      return( m_blue >= m_red )
+    }
+  }
+}