seq()函数

函数功能：

Generate regular sequences. 

产生序列

函数语法：

seq(from = 1, to = 1, by = ((to - from)/(length.out - 1)),
    length.out = NULL, along.with = NULL, ...)

函数参数：

from, to	
the starting and (maximal) end values of the sequence. 
Of length 1 unless just from is supplied as an unnamed argument.

序列的起始值和结束值。

by	
number: increment of the sequence.

步长：序列的增量

length.out	
desired length of the sequence. A non-negative number, 
which for seq and seq.int will be rounded up if fractional.

序列的长度，非负数值；若为小数进行四舍五入

along.with	
take the length from the length of this argument.

与哪个变量长度相同

官方文档seq( )函数