ARRGEN

Purpose

This function is similar to (and an extension of) built-in
functions like indgen, findgen, etc. It creates an array given the
first element, last element, and step size. It can create arrays
which increase/decrease by constant amounts at each element, or
that increase/decrease by constant factors at each element.

Calling Sequence

result = ARRGEN(first, max, [step, /log, nstep = nstep])

Inputs

first: The first element in the array. The data type of the result
will be the same as first
last: The (approximate) last element in the array. If there are not
an integer number of elements between first and last, then
one extra element will be added. In other words, either the
last element will have the value "last", or the last two
elements will bracket the value "last."
step: The difference between adjacent array elements. If /LOG is
not set, this must be a positive number, and specifies the
additive offset between adjacent elements. If /LOG is set,
this must be a number greater than one. It specifies the
multiplicative offset between adjacent elements.

Keyword Parameters

LOG: If set, then the array values increase or decrease by a
multiplicative (instead of additive) constant at each step. In
otherwords, the logarithm of the elements are evenly spaced.
NSTEP: Set to specifiy the number of elements in the array, instead
of the step size. This overrides step.

Outputs

The created array.

Example

IDL> print, arrgen(1, 5, 1)
1 2 3 4 5
IDL> print, arrgen(1, 10, 4)
1 5 9 13
IDL> print, arrgen(5, 1, 2)
5 3 1
IDL> print, arrgen(1, 1000, 10, /log)
1 10 100 1000
IDL> print, arrgen(1.0D, 5, 1)
1.0000000 2.0000000 3.0000000 4.0000000 5.0000000

Modification History

July 2009: Written by Chris Beaumont
July 2009: Added nstep keyword