Wednesday, 1 August 2018

Data Management : Sequences in R Language

Sequences

The regular sequences can be generated in R.

Syntax :-

seq ( )

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

Examples:

> seq (10)
   [1]  1  2  3  4  5  6  7  8  9  10

is the same as
> seq (1 : 10)



Assignment of an index-vector

> x <- c (9,8,7,6)
> ind <- seq (along = x)
> ind
   [1]  1 2 3 4


Accessing a value in the vector through index vector
→ Accessing an element of an index-vector
> x [ind [2] ]
   [1] 8 


Generating sequence of dates

Generating current time and date

Sys.time ( )  command provides the current time and date from the computer system.
> Sys.time ( )
  [1]  "2017-01-01  09:17:01  IST"

Sys.Date ( ) command provides the current date from the computer system.
> Sys.Date ( )
    [1]  "2017-01-01"

Usage
seq (from, to, by, length.out = NULL, along.with = NULL, ...)

Arguments
from             starting date (Required)
to                  end date (Optional)
by                 Increment of the sequence.  "day" , "week" , "month" , "quarter" or "year".
length.out     Integer, optional. Desired length of the sequence.
along.with    take the length from the length of this argument.

Sequence of first day of years

> seq (as.Date ("2010-01-01") , as.Date ("2017-01-01"), by = "Years")
[1] "2010-01-01"  "2011-01-01"  "2012-01-01"  "2013-01-01"
[5] "2014-01-01"  "2015-01-01"  "2016-01-01"  "2017-01-01"


Sequence of days

> seq (as.Date ("2017-01-01") , by = "days", length = 6)


Sequence of months

> seq (as.Date ("2017-01-01") , by = "days", length = 6)



Sequence of years

> seq (as.Date ("2017-01-01") , by = "years", length = 6)



To find sequence with defining start and end dates

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