Upload R code for week 4.

weeks/week4/README.md

@@ -48,7 +48,6 @@ abline(h = mean(d), col = "red", lty = 2)
 
 # show lines from each of our points to the mean
 for (i in 1:length(d)) {
-  print(paste(c(i, i), c(d[i], mean(d))))
   lines(c(i, i), c(d[i], mean(d)), col = "blue")
 }
 
@@ -75,4 +74,4 @@ degrees_of_freedom <- length(d) - 1
 mean_squared_residuals <- sum_of_squares / degrees_of_freedom
 ```
 
-Now we will compute the variance by hand.
+Now we will compute the variance by hand, using the code above!

weeks/week4/week4.R

@@ -0,0 +1,32 @@
+x <- c(1, 2, 3, 4, 5, 10, 1000)
+
+# edit your median function so that it works
+# for both even and odd length vectors
+my.median <- function(x) {
+  # is the vector even length??
+  is_vector_even <- length(x) %% 2 == 0
+  # sort
+  sorted_vec <- sort(x)
+  # get the mid point
+  index_of_mid_point <- length(sorted_vec) / 2
+
+  if (is_vector_even) {
+    # ...
+    first_midpoint <- sorted_vec[index_of_mid_point]
+    second_midpoint <- sorted_vec[index_of_mid_point + 1]
+
+    return((first_midpoint + second_midpoint) / 2)
+  } else {
+    to_integer <- ceiling(index_of_mid_point)
+    first_midpoint <- sorted_vec[to_integer]
+    return(first_midpoint)
+  }
+}
+
+vec <- c(1, 2, 3, 4, 5, 10) # 3.5
+vec2 <- c(1, 2, 3, 4, 5, 10, 1000) # 4
+
+my.median(vec2)
+median(vec2)
+
+my.median(vec2) == median(vec2)