【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