【统计与建模】R语言基本操作

 # vec <- rep( seq(1,5,by=0.5),3)

 # vec <- seq( 1 , 10 , by = 1 )
 # min(vec)  #最小值
 # max(vec)  #最大值
 # range(vec)  #范围
 # length(vec) #长度
 # sum(vec)  #总和
 # prod(vec) #向量元素所有的乘积
 # median(vec) #中位数
 # mean(vec) #均值
 # var(vec) #样本方差
 # sort(vec) #排序
 # order(-vec) #排序 的是 索引并不改变向量的实际位置
 # vec

 # vec <- 1:5
 # Logic_vec <- vec > 3
 # Logic_vec

 # str = c( "x" , "y" , "z" , "w" )
 # paste("result.",str,sep="")

 # x <- -5 : 5
 # y <- numeric( length(x) )
 # y[x<0] <- 1 - x[x<0]
 # y[x>=0] <- 1 + x[x>=0]
 # x;y

 # sex <- c("M","F","M","M","F");sex

 # sexf <- factor(sex) ; sexf 

 # sex.level <- levels(sexf) ; sex.level

 # sex.tab <- table( sexf ) ; sex.tab 

 # sex <- c("M","F","M","M","F")
 # sexf <- factor(sex);
 # sex.level <- levels(sexf);
 # height <- c(174,165,180,171,160)
 # tapply( height , sex , mean )

 # A <- matrix( 1:9 , nrow = 3 , ncol = 3 , byrow = TRUE ) ;
 # A[3,3] = 10;A;
 # B <- matrix( 1 , nrow = 3 , ncol = 1 , byrow = TRUE ) ; B 

 # A <- matrix( 1:9 , nrow = 3 , ncol = 3 , byrow = TRUE ) ;
 # A[3,3] = 10;
 # det(A)

 # A <- t( array( c(1:8,10) , dim=c(3,3) ) );A
 # Inv_A <- solve(A) ; Inv_A

 # A <- t( array( c(1:8,10) , dim=c(3,3) ) );A
 # Inv_A <- solve(A) ; Inv_A
 # E = A %*% Inv_A ; E 

 # A <- t( array( c(1:8,10) , dim = c(3,3) ) );A
 # b <- c( 1 , 1 , 1 );b
 # x <- solve( A,b ) ; x 

 # A <- t( array( c(1:8,10) , dim = c(3,3) ) );A
 # Sm <- tcrossprod (A,A); Sm

 # ev <- eigen(Sm) ; ev

 # A <- t( array( c(1:8,10) , dim = c(3,3) ) );A
 # svdA <- svd(A) ; svdA
 # u = svdA$u;u
 # v = svdA$v;v
 # d = svdA$d;d
 # u %*% diag(d)  %*% t(v)

 # A <- t( array( c(1:8,10) , dim = c(3,3) ) );A
 # apply( A , 2 , sum )

 # fzero <- function( f , a , b , eps = 1e-5 ){
 #     if( f(a) * f(b) > 0 )
 #         list( fail = "Unfound ")
 #     else{
 #         repeat{
 #             if( abs(b-a) < eps ) break
 #             x <- (a+b) / 2
 #             if( f(a) * f(x) < 0 ){
 #                 b <- x
 #             }
 #             else{
 #                 a <- x
 #             }
 #         }
 #         list(root = (a+b)/2,fun = f(x) )
 #     }
 # }
 #
 # f <- function( x ) { x^3 - x - 1 }
 # fzero(f,0,10,1e-6)

 # area <- function( f , a , b , eps = 1e-6 , lim = 10 ){
 #     fun1 <- function( f , a , b , fa , fb , a0 , eps , lim , fun ){
 #         d <- ( a+b ) / 2 ;
 #         h <- ( b-a ) / 4 ;
 #         fd <- f(d) ;
 #         a1 <- h * ( fa+fd )
 #         a2 <- h * ( fd+fb )
 #         if( abs(a0-a1-a2) < eps || lim == 0 ){
 #             return ( a1 + a2 )
 #         }else{
 #             return ( fun(f,a,d,fa,fd,a1,eps,lim-1,fun)
 #                     +fun(f,d,b,fd,fb,a2,eps,lim-1,fun))
 #         }
 #     }
 #     fa <- f(a);
 #     fb <- f(b);
 #     a0 <- ((fa+fb) * (b-a))/2;
 #     fun1(f,a,b,fa,fb,a0,eps,lim,fun1)
 # }
 #
 # f <- function(x) x
 # quad <- area(f,0,10) ; quad