User:Karenlee

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Sequence(start, end, step)

Creates a list of numbers increasing or decreasing from start to end by increments (or decrements) of step. step is optional and defaults to 1. Sequence is commonly used to define Indexes, such as a list of integers or dates in ascending order.

The parameters start, end, and step must be deterministic scalar numbers, not arrays. See Expressions that don't array-abstract.

You can also select this function using the Sequence option from the expr menu.

The expression m .. n using the operator ".." is equivalent to Sequence(m, n, 1).

Examples

If end is greater than start, the sequence is increasing: 

Sequence(1,5) →
List View Expression View
IMAGE of List View [1,2,3,4,5]

If start is greater than end, the sequence is decreasing: 

Sequence(5,1) → [5, 4, 3, 2, 1]

Unless strict is true: 

Sequence(5, 1, strict:true) → []
Sequence(5, 1, -2, strict:true)  → [5, 3, 1]

If start=> and end are not integers, and you omit stepSize, it rounds them: 

Sequence(1.2, 4.8) → [1, 2, 3, 4, 5]

If you specify stepSize, it can create non-integer values: 

Sequence(0.5, 2.5, 0.5) → [0.5, 1, 1.5, 2, 2.5]

Optional parameters

strict

Normally, if start > end, and step is positive, the sequence decrements by step. As a result of this convention, a sequence will always have at least one element.

There are cases where a strict sequence is desired, such that the sequence proceeds from start in increments of step, according to the sign of step. When step proceeds in the direction away from ‘’’’’end’’’’’, then a zero-length sequence results. For example, in a For..Do loop, you may want zero iterations when end is less than start. Specifying the optional parameter strict as true obtains a strict Sequence, e.g. 

Sequence(x1,x2,strict:true)

When strict is specified as true, the step may be negative, and must be negative to obtain a decreasing sequence.

dateUnit

If you want to create a sequence of dates or times, successive days or hours, the first day of each week, month, or year, and so on, you can set the optional dateUnit parameter to the relevant date/time character. For example, 

Sequence( MakeDate(2009,1,1), MakeDate(2010,12,31), 4, dateUnit:"M" ) 
→ [ 1-Jan-2009, 1-May-2009, 1-Sep-2009, 1-Jan-2010, 1-May-2010, 1-Sep-2010 ]

These are the characters defining each date and time unit:

  • Years (dateUnit:'Y')
  • Months ('M')
  • Days ('D' this is the default if dateUnit is omitted)
  • Weekdays ('WD')
  • Hours ('h')
  • minutes ('m')
  • seconds ('s').

Character Sequences

The start and end characters may be single characters. In this case, a sequence of characters following ASCII order is returned.

Sequence('T','f') → ['T','U','V','W','X','Y','Z','[','\',']','^','_','`','a','b','c','d','e','f']
Sequence('!','@') → ['!','""','#','$','%','&',''','(',')','*','+',',','-','.','/','0','1','2','3','4','5','6','7','8','9',':',';','<','=','>','?','@']

Spreadsheet Column Name Sequences

When start and end are multi-letter sequences, containing only letters, with all letters having the same upper-case or lower-case, then a spreadsheet column sequence is returned.

These sequences are letter sequences that go from 'A'..'Z', then from 'AA'..'AZ', 'BA'..'BZ', ... 'ZA'..'ZZ', then 'AAA'..'ZZZ', 'AAAA'..'ZZZZ', etc., up to six digits total.

Sequence('W','AF') → ['W','X','Y','Z','AA','AB','AC','AD','AE','AF']

For these sequences, the start and stop must consist entirely of letters, and all letters must be all upper case or all lower case.


History

  • Analytica 4.4 or patch 4.3.3
    • Spreadsheet column name sequences
    • Character sequences
  • Analytica 4.2
    • Strict sequences
    • Date sequences

Table Test Formatting

On the Left

MDTable(T,Rows,Cols,[Car_type,Mpg],'average','n/a') →
Mpg ▶
Car_type ▼ 26 30 35
VW 2185 1705 n/a
Honda 2330 n/a 2210
BMW n/a 2955 2835

On Top

MDTable(T,Rows,Cols,[Car_type,Mpg],'average','n/a') →

Mpg ▶
Car_type ▼ 26 30 35
VW 2185 1705 n/a
Honda 2330 n/a 2210
BMW n/a 2955 2835

MH Test

MDTable(T,Rows,Cols,[Car_type,Mpg],'average','n/a') →

Mpg ▶
Car_type ▼ 26| 30|35|- VW 2185 1705 n/a
Honda 2330 n/a 2210
BMW n/a 2955 2835