R统计软件.pptVIP

函数rep用来创建一个所有元素都相同的向量 函数sequence创建一系列连续的整数序列，每个序列都以给定参数的数值结尾 * * * * * * * * * * * * * * * * * * * * * * * * * [ ] index :: access variables in a name space $ component extraction attach() names() test1-read.table(c:/test.csv, header=T, sep=,); test1[1,] ; test1[,2]; test1[,2, drop=F ] test1[-1,] test1[test1=170] mtcars sum(x) sum of the elements of x prod(x) product of the elements of x max(x) maximum of the elements of x min(x) minimum of the elements of x which.max(x) returns the index of the greatest element of x which.min(x) returns the index of the smallest element of x range(x) in. than c(min(x),max(x)) length(x) number of elements of x mean(x) mean of the elements of x median(x) median of the elements of x var(x) or cov(x) variance of the elements of x (calculated on n-1);if x is a matrix or a data frame, the variance-covariance matrix is calculated cor(x) correlation matrix of x if it is a matrix or a data frame(1 if x is a vector) var(x,y) or cov(x,y) covariance between x and y, or between the columns of x and those of y if they are matrices or data frames cor(x,y) linear correlation between x and y, or correlation matrix if they are matrices or data frames choose(n,k) computes the combinations of k event among n repetitions = n! / [(n-k)!k!] na.omit(x) suppresses the observations with missing data(NA) (suppresses the corresponding line if x is a matrix or a data frame) na.fail(x) returns an error message if x contains at least one NA unique(x) if x is vector or a data frame, return a similar object but with the duplicate elements suppressed table(x) returns a table with the numbers of the differents values of x (typically for integers or factors) table(x,y) contingency table of x and y subset(x,…) returns a selection of x with respect to criteria (…, typically comparison: x$v1 10); if x is a data frame, the option select gives the variables to be kept (or dropped using a minus sign) sample(x,size) resample randomly and without replacement size e