- 20150921 [Coursera] R Programming (6)
- 整理自 R Programming (Week 1) -- Vectorized Operations
- [ Week 1 課程內容 ]
- [ 本次筆記內容 ]
- [ 補充資料 ]
- （一）Vectorized Operations
- [ 重點整理 ] R 語言的特性
- 1. 向量化運算
- 2. 矩陣的向量化運算
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整理自 R Programming (Week 1) -- Vectorized Operations
Introduction(略過)Overview and History of R[16:07](完成)Getting Help[13:53] (略過)Console Input and Evaluation[4:46](完成)Data Types - R Objects and Attributes[4:43](完成)Data Types - Vectors and Lists[6:27](完成)Data Types - Matrices[3:24](完成)Data Types - Factors[4:31](完成)Data Types - Missing Values[2:10](完成)Data Types - Data Frames[2:44](完成)Data Types - Names Attribute[1:49](完成)Data Types - Summary[0:43](完成)Reading Tabular Data[5:51](完成)Reading Large Tables[7:08](完成)Textual Data Formats[4:58](完成)Connections: Interfaces to the Outside World[4:35](完成)Subsetting - Basics(完成)Subsetting - Lists(完成)Subsetting - Matrices(完成)Subsetting - Partial Matching(完成)Subsetting - Removing Missing Values(完成)Introduction to swirl(略過)（一）Vectorized Operations
> x <- 1:4; y <- 6:9 # 建立"x","y"這兩個向量(x: 1~4, y: 6~9)>> # 加法> x + y # 進行相加("1+6" "2+7" "3+8" "4+9")[1] 7 9 11 13>> # 邏輯判斷> x > 2 # 判斷"x"是否大於"2"，會得到邏輯結果(TRUE or FALSE)[1] FALSE FALSE TRUE TRUE> x >= 2 # 判斷"x"是否大於等於"2"，會得到邏輯結果(TRUE or FALSE)[1] FALSE TRUE TRUE TRUE> y == 8 # 判斷"x"是否等於"8"，會得到邏輯結果(TRUE or FALSE)[1] FALSE FALSE TRUE FALSE>> # 乘法> x * y # 進行相乘("1*6" "2*7" "3*8" "4*9")[1] 6 14 24 36>> # 除法> x / y # 進行相除("1/6" "2/7" "3/8" "4/9")[1] 0.1666667 0.2857143 0.3750000 0.4444444> # 建立"x","y"這兩個矩陣> x <- matrix(1:4, 2, 2) # x: 從1~4,是個2x2的矩陣> y <- matrix(rep(10, 4), 2, 2) # y: 有4個10,是個2x2的矩陣> x [,1] [,2][1,] 1 3[2,] 2 4> y [,1] [,2][1,] 10 10[2,] 10 10>>> ## 矩陣內元素的運算> x * y # 這不是矩陣乘法,這是按照矩陣裡的元素相乘 [,1] [,2][1,] 10 30[2,] 20 40>> x / y # 這不是矩陣除法,這是按照矩陣裡的元素相除 [,1] [,2][1,] 0.1 0.3[2,] 0.2 0.4>>> ## 矩陣的運算> x %*% y # 矩陣相乘("%*%") [,1] [,2][1,] 40 40[2,] 60 60