网站建设与设计试题,陈江做网站,织梦茶叶网站模板免费下载,阿里巴巴免费做网站吗文章目录 matchpmatchcharmatch match
?matchDescription
match returns a vector of the positions of (first) matches of its first argument in its second.
第一个向量中的元素在第二个向量中的位置#xff0c;如果第二个向量中有多个仅返回第一个match 元素的位置如果第二个向量中有多个仅返回第一个match 元素的位置第二个向量中不存在则返回NULL%in% is a more intuitive interface as a binary operator, which returns a logical vector indicating if there is a match or not for its left operand.操作符 %in% 是match的简易变形版本返回结果为TRUE,FALSEUsage
match(x, table, nomatch NA_integer_, incomparables NULL)x %in% tableArguments
x vector or NULL: the values to be matched. Long vectors are supported.table vector or NULL: the values to be matched against. Long vectors are not supported.nomatch the value to be returned in the case when no match is found. Note that it is coerced to integer.
如果没有match应该返回什么值默认是NULLincomparables a vector of values that cannot be matched. Any value in x matching a value in this vector is assigned the nomatch value. For historical reasons, FALSE is equivalent to NULL.
类似于排除第一个向量中的某些元素当第一个向量中的某些元素match 该参数指定的向量时则返回NULL。Examples
# 取两个向量的交集
intersect - function(x, y) y[match(x, y, nomatch 0)]
intersect(1:10, 7:20)1:10 %in% c(1,3,5,9)
sstr - c(c,ab,B,bba,c,NA,,bla,a,Ba,%)
sstr[sstr %in% c(letters, LETTERS)]pmatch
?pmatchDescription
pmatch seeks matches for the elements of its first argument among those of its second.Usage
pmatch(x, table, nomatch NA_integer_, duplicates.ok FALSE)Arguments
x the values to be matched: converted to a character vector by as.character. Long vectors are supported.table the values to be matched against: converted to a character vector. Long vectors are not supported.nomatch the value to be returned at non-matching or multiply partially matching positions. Note that it is coerced to integer.duplicates.ok should elements be in table be used more than once?
这个参数控制该函数的行为决定第二个向量中可以match几次是遇到第一个match的就终止match还是寻找所有可以match的Examples
pmatch(, ) # returns NA
pmatch(m, c(mean, median, mode)) # returns NA --- 更具这一个示例我觉得还是不要考虑使用这个函数了通常我们会认为应该返回一个位置的但返回了NA容易给人造成误导。
pmatch(me,c(mean, median, mode),duplicates.ok TRUE) # returns NA
pmatch(med, c(mean, median, mode)) # returns 2pmatch(c(, ab, ab), c(abc, ab), dup FALSE)
pmatch(c(, ab, ab), c(abc, ab), dup TRUE)
## compare
charmatch(c(, ab, ab), c(abc, ab))charmatch
?charmatchDescription
charmatch seeks matches for the elements of its first argument among those of its second.Usage
charmatch(x, table, nomatch NA_integer_)Arguments
x the values to be matched: converted to a character vector by as.character. Long vectors are supported.table the values to be matched against: converted to a character vector. Long vectors are not supported.nomatch the (integer) value to be returned at non-matching positions.if multiple exact or multiple partial matches are found then 0 is returned and if no match is found then nomatch is returned.
Examples
charmatch(, ) # returns 1
charmatch(m, c(mean, median, mode)) # returns 0
charmatch(med, c(mean, median, mode)) # returns 2
