SEQUENCE

SEQUENCE (LET)

Let Subcommand

Generate a sequence of values.

This command is useful for generating variables that have constant increments. Increments can be either positive or negative. Increments can also be real numbers (i.e., they are not restricted to integers).

Specifically, you specify a start value, an increment, and a stop value. You can also optionally specify a repeat factor (this defaults to 1 if not specified).

The 2010/11 version of Dataplot updated this command to support variable arguments for the start, increment, stop, and repeat factors. If more than one of these is a variable (as oppossed to a constant/parameter), then these variable must have the same length. If a variable is used for one or more of the arguments, then we essentially create k separate sequences (where k is the number of elements in the variable) and append the results together. Arguments that are entered as constants or parameters will use the same value for each sequence.

In addition, a new syntax was added where the first argument is a list of values and the second argument is the number of times that each value is repeated. This syntax is useful when you want to generate a simple sequence with repeat values where the number of repeats is variable.

See the Note section below for some examples of using this new syntax.

LET <resp> = SEQUENCE <start> <inc> <stop>
where <start> is a constant, parameter, or variable that specifies the beginning value for the sequence;
            <inc> is a constant, parameter, or variable that specifies the increment value of the sequence;
            <stop> is a constant, parameter, or variable that specifies the ending value of the sequence;
and <resp> is a variable where the generated sequence is saved.

This is the most common syntax for this command.

LET <resp> = SEQUENCE <start> <inc> <stop>
                        FOR I = <start2> <inc2> <stop2>
where <start> is a constant, parameter, or variable that specifies the beginning value for the sequence;
            <inc> is a constant, parameter, or variable that specifies the increment value of the sequence;
            <stop> is a constant, parameter, or variable that specifies the ending value of the sequence;
            <start2> is a number or parameter that identifies the first row of <resp> in which the sequence is saved (typically it has a value of 1);
            <inc2> is a number or parameter that identifies the row increment of <resp> in which the sequence is saved (typically it has a value of 1);
            <stop2> is a number or parameter that identifies the last row of <resp> in which the sequence is saved;
and <resp> is a variable where the generated sequence is saved.

This syntax is similar to syntax 1 except that the generated sequence is repeated until the rows of are filled as specified by the FOR clause.

LET <resp> = SEQUENCE <start> <repeat> <inc> <stop>
where <start> is a constant, parameter, or variable that specifies the beginning value for the sequence;
            <repeat> is a constant, parameter, or variable that specifies the number of times each value in the sequence is repeated;
            <inc> is a constant, parameter, or variable that specifies the increment value of the sequence;
            <stop> is a constant, parameter, or variable that specifies the ending value of the sequence;
            and <resp> is a variable where the generated sequence is saved.

This syntax is useful for generating sequence like 1 1 1 2 2 2 3 3 3 4 4 4.

LET <resp> = SEQUENCE <start> <repeat> <inc> <stop>
                        FOR I = <start2> <inc2> <stop2>
where <start> is a constant, parameter, or variable that specifies the beginning value for the sequence;
            <repeat> is a constant, parameter, or variable that specifies the number of times each value in the sequence is repeated;
            <inc> is a constant, parameter, or variable that specifies the increment value of the sequence;
            <stop> is a constant, parameter, or variable that specifies the ending value of the sequence;
            <start2> is a number or parameter that identifies the first row of <resp> in which the sequence is saved (typically it has a value of 1);
            <inc2> is a number or parameter that identifies the row increment of <resp> in which the sequence is saved (typically it has a value of 1);
            <stop2> is a number or parameter that identifies the last row of <resp> in which the sequence is saved;
and <resp> is a variable where the generated sequence is saved.

This syntax is similar to syntax 3 except that the generated sequence is repeated until the rows of are filled as specified by the FOR clause.

LET <resp> = SEQUENCE <values> <repeat>
where <values> is a constant, parameter, or variable that specifies the values for the sequence;
            <repeat> is a constant, parameter, or variable that specifies the number of times each value in <values> is repeated;
and <resp> is a variable where the generated sequence is saved.

This syntax is useful when the number of repeated values varies. For example, you can do something like

LET VAL = SEQUENCE 1 1 5
LET REP = DATA 3 3 2 4 4


to generate the sequence
1 1 1 2 2 2 3 3 4 4 4 4 5 5 5 5

LET X = SEQUENCE 1 1 100
LET X = SEQUENCE 1 1 10 FOR I = 1 1 100
LET X = SEQUENCE -4 9 1 4
LET X = SEQUENCE 1 50 1 2 FOR I = 1 1 100

To generate the sequence
1, 2, 3, 4, 5, 31, 32, 33, 61, 62, 63, 64, 65, 66, 67

you can enter the commands

LET START = DATA 1 31 61
LET STOP = DATA 5 33 67
LET Y = SEQUENCE START 1 STOP


To generate the sequence

1 1 1 2 2 3 3 3 3 4 4 4 4 4

you can enter the command

LET VAL = SEQUENCE 1 1 4
LET REP = DATA 3 2 4 5
LET Y = SEQUENCE VAL REP


Additional examples of using the variables with the SEQUENCE command are given in the Program section below.

None

The word SEQUENCE can be omitted from the command.

PATTERN	= Generate numbers with a specific pattern.
DATA	= Place numbers in a variable.
COMBINE	= Combine constants, parameters, and variables into a single variable.
FIBONNACCI NUMBERS	= Generate Fibonnacci numbers.
LOGISTIC NUMBERS	= Generate numbers from a logistic sequence.

Data Management

Pre-1987
2010/11: Added support for variables as arguments
2010/11: Added support for Syntax 5

 
LET X = SEQUENCE -4 1 4 FOR I = 1 1 81
LET Y = SEQUENCE -4 9 1 4
LET Z = X**2+Y**2-X*Y
LET Z0 = SEQUENCE 5 5 40
CONTOUR PLOT Z X Y Z0
    

 
set write decimals 1
.
.  Step 1: First test basic current usage
.
let y = sequence 1 1 10
print y


---------------
              Y
---------------
            1.0
            2.0
            3.0
            4.0
            5.0
            6.0
            7.0
            8.0
            9.0
           10.0


pause
delete y
.
let y = sequence 1 3 1 10
print y


---------------
              Y
---------------
            1.0
            1.0
            1.0
            2.0
            2.0
            2.0
            3.0
            3.0
            3.0
            4.0
            4.0
            4.0
            5.0
            5.0
            5.0
            6.0
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            7.0
            8.0
            8.0
            8.0
            9.0
            9.0
            9.0
           10.0
           10.0
           10.0


pause
delete y
.
.  Step 2: Now test "variable" syntax
.
let rep = data 1 2 3 1 2 3 1 2 3 1
let y = sequence 1 rep 1 10
print y


---------------
              Y
---------------
            1.0
            2.0
            3.0
            4.0
            5.0
            6.0
            7.0
            8.0
            9.0
           10.0
            1.0
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           10.0


pause
delete y rep
.
let stop = sequence 10 1 1
let y = sequence 1 2 1 stop
print y

---------------
              Y
---------------
            1.0
            1.0
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            1.0
            1.0


pause
delete y stop
.
let start = data 1 100 1000
let inc   = data 1  10  100
let stop  = data 10 1000 10000
let rep   = data 3 2 1
let y = sequence start rep inc stop
print y


---------------
              Y
---------------
            1.0
            1.0
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         9300.0
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         9900.0
        10000.0


pause
delete y start rep inc stop
.
let start = data 1 2 3 4 5
let rep   = data 5 3 1 4 2
let y = sequence start rep
print y


---------------
              Y
---------------
            1.0
            1.0
            1.0
            1.0
            1.0
            2.0
            2.0
            2.0
            3.0
            4.0
            4.0
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            4.0
            5.0
            5.0


pause
delete y start rep