ysw <- matrix(c(94,98,85,85,97,95, 96,98,96,96,98,95, 95,98,85,82,96,93), ncol = 3, dimnames = list( c("张三","李四","王五","悟空","八戒","沙僧"), c("yw","sx","wy") ) ) # 按列填充 ysw ysw <- matrix(c(94,98,85,85,97,95, 96,98,96,96,98,95, 95,98,85,82,96,93), ncol = 3) # 按列填充 colnames(ysw)<-c("yw","sx","wy") row.names(ysw) <- c("张三","李四","王五","悟空","八戒","沙僧") ysw # yw sx wy # 张三 94 96 95 # 李四 98 98 98 # 王五 85 96 85 # 悟空 85 96 82 # 八戒 97 98 96 # 沙僧 95 95 93 ysw <- matrix(c(94,96,95, 98,98,98, 85,96,85, 85,96,82, 97,98,96, 95,95,93), byrow = TRUE,# 按行填充 ncol = 3) colnames(ysw)<-c("yw","sx","wy") row.names(ysw) <- c("张三","李四","王五","悟空","八戒","沙僧") ysw # yw sx wy # 张三 94 96 95 # 李四 98 98 98 # 王五 85 96 85 # 悟空 85 96 82 # 八戒 97 98 96 # 沙僧 95 95 93
colnames(ysw) # [1] "yw" "sx" "wy" row.names(ysw) # [1] "张三" "李四" "王五" "悟空" "八戒" "沙僧" nrow(ysw) # [1] 6 ncol(ysw) # [1] 3 dim(ysw) # [1] 6 3 dimnames(ysw) # [[1]] # [1] "张三" "李四" "王五" "悟空" "八戒" "沙僧" # [[2]] # [1] "yw" "sx" "wy"
ysw[5,] # 通过下标 ysw['八戒',] # 通过名称 # yw sx wy # 97 98 96 ysw[5,-3] ysw[5,1:2] # 第一行后两个 # yw sx # 97 98
ysw[,c("sx","yw","wy")] # sx yw wy # 张三 96 94 95 # 李四 98 98 98 # 王五 96 85 85 # 悟空 96 85 82 # 八戒 98 97 96 # 沙僧 95 95 93
order_sx <- order(ysw[,'sx'],decreasing = TRUE) order_sx # [1] 2 5 1 3 4 6 ysw[order_sx,] # yw sx wy # 李四 98 98 98 # 八戒 97 98 96 # 张三 94 96 95 # 王五 85 96 85 # 悟空 85 96 82 # 沙僧 95 95 93
ysw2 <- matrix(c(88,89,89,96,95,96), ncol = 3, dimnames = list( c("刘备","曹操"), c("yw","sx","wy") )) ysw2 # scff sx wy # 刘备 88 89 95 # 曹操 89 96 96 rowAdd <- rbind(ysw,ysw2) rowAdd # yw sx wy # 张三 94 96 95 # 李四 98 98 98 # 王五 85 96 85 # 悟空 85 96 82 # 八戒 97 98 96 # 沙僧 95 95 93 # 刘备 88 89 95 # 曹操 89 96 96
lszz <- matrix(c(88,98,85,85,97,95, 96,98,96,96,98,95), ncol = 2, dimnames = list( c("张三","李四","王五","悟空","八戒","沙僧"), c("ls","zz") ) ) lszz # ls zz # 张三 88 96 # 李四 98 98 # 王五 85 96 # 悟空 85 96 # 八戒 97 98 # 沙僧 95 95 colAdd <- cbind(ysw,lszz) colAdd # yw sx wy ls zz # 张三 94 96 95 88 96 # 李四 98 98 98 98 98 # 王五 85 96 85 85 96 # 悟空 85 96 82 85 96 # 八戒 97 98 96 97 98 # 沙僧 95 95 93 95 95
rowSums(ysw) apply(ysw, 1,sum) # 张三 李四 王五 悟空 八戒 沙僧 # 285 294 266 263 291 283 colMeans(ysw) apply(ysw,2 ,mean) # yw sx wy # 92.33333 96.50000 91.50000 apply(ysw,2 ,function(x){ sd(x)/mean(x) }) # yw sx wy # 0.06339827 0.01269166 0.07074340
apply split->apply-combine: 先分组对每一组操作组合
A <- matrix(c(1,2,3, 2,2,5, 3,5,1), ncol = 3, byrow = TRUE) b <- 1:3 solve(A,b) # [1] 1 0 0
图片alt
R与matlab对照
An <- diag(3) # cAn # [,1] [,2] [,3] # [1,] 1 0 0 # [2,] 0 1 0 # [3,] 0 0 1 solve(A,An) # [,1] [,2] [,3] # [1,] -1.5333333 0.86666667 0.26666667 # [2,] 0.8666667 -0.53333333 0.06666667 # [3,] 0.2666667 0.06666667 -0.13333333 solve(A) %*% A # 得到单位矩阵 # [,1] [,2] [,3] # [1,] 1.000000e+00 8.881784e-16 1.054712e-15 # [2,] -4.440892e-16 1.000000e+00 -7.077672e-16 # [3,] -5.551115e-17 -1.110223e-16 1.000000e+00
sqrt(2)^2 == 2 # FALSE dplyr::near(sqrt(2)^2,2) # TRUE all(dplyr::near(solve(A) %*% A,diag(3))) # TRUE
矩阵本质就是二维数组
install.packages('imager', repos ="https://mirrors.tuna.tsinghua.edu.cn/CRAN/")
Ubuntu 需要安装 sudo apt-get install libfftw3-dev libtiff5-dev
sudo apt-get install libfftw3-dev libtiff5-dev
library(imager) img1 <- load.image("/home/wy/Pictures/7777777.jpg") str(img1) # cimg [1:640, 1:427, 1, 1:3] plot(img1) img1[,,1]<-0 # 去掉红色图层 img1[,,3]<-0 # 去掉蓝色图层 plot(img1)
area_coor_x <- 350:449 area_coor_y <- 110:259 array_dim <- c(length(area_coor_x),length(area_coor_y),3) array_dim # [1] 100 150 3 array_data <- runif(prod(array_dim)) array_data random_noise <- array(dim = array_dim,data = array_data) random_noise img1[area_coor_x,area_coor_y,]<- (1-0.6) * img1[area_coor_x,area_coor_y,]+ 0.6*random_noise plot(img1)
注意：硬盘上的任何数据都是R的六种数据(向量，因子，矩阵，数组，数据框，列表)之一