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--- r:basics [2019/09/19 12:02] – [Basic (descriptive) Statistics] hkimscil
+++ r:basics [2019/09/25 10:32] (current) – [Performing Vector Arithmetic] hkimscil
@@ Line 156: / Line 156: @@
 [1] 11.49988
 </code>
+$$ r = \frac {\text{covariance (x, y)}}  {sd(x) * sd(y)} $$
 <code>
@@ Line 191: / Line 193: @@
 </code>
 </WRAP>
+<code>
+> dlist <- list(small,medium,big)
+> dlist
+[[1]]
+ [1] 0.6739635 1.5524619 0.3250562 1.2143595 1.3107692 2.1739663
+ [7] 1.6187899 0.8872657 1.9170283 0.7767406
+[[2]]
+ [1] 10.526448  9.205156 11.427756  8.533180  9.763317  9.806662
+ [7]  9.150245 10.058465  9.182330  7.949692
+[[3]]
+ [1]  99.83624 100.70852  99.73202  98.53608 100.74444  98.58961
+ [7] 100.46707  99.88068 100.46724 100.49814
+> lapply (dlist,mean)
+[[1]]
+[1] 1.24504
+[[2]]
+[1] 9.560325
+[[3]]
+[1] 99.946
+> sapply(dlist, sd)
+[1] 0.5844025 0.9920282 0.8135503
+</code>
 <code>
@@ Line 258: / Line 288: @@
 </code>
+sequence (''seq'') 는 x축의 구성을 임의적으로 만들 때 유용. 예를 들면, normal distribution graph 등.
+<code>
+x <- seq(-4, 4, length=10000)
+y <- dnorm(x, mean=0, sd=1)
+plot(x, y, type="l", lwd=1)
+</code>
 ====== Comparing Vectors ======
 <code>> a <- 3
@@ Line 389: / Line 426: @@
 ====== Performing Vector Arithmetic ======
+see [[:social network analysis]]
 <code>> v <- c(11,12,13,14,15)
 > w <- c(1,2,3,4,5)
@@ Line 417: / Line 456: @@
 [1] -1.2649111 -0.6324555  0.0000000  0.6324555  1.2649111
 </code>
+<WRAP box help>get variance of v without using var() function.
+</WRAP>
 <code>> w
@@ Line 447: / Line 489: @@
 | <- <<-  | Assignment (right to left)  | Recipe 2.2  |
 | ?   | Help  | Recipe 1.7  |
 <code>%%
@@ Line 487: / Line 528: @@
 <WRAP box help>
 fill values less than 2 with zeros in stu matrix
+<code> stu[stu < 3] <- 0 </code>
 </WRAP>