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Program: CREATE

Purpose: Creates a SET (and subsets)

Category: UTILITY

File: create.shl

Author: K.G. Begeman

Keywords:

OUTSET= Name of set to create.
If the set already exists, the user is asked whether
the set should be deleted with DELETE=

DELETE= Delete this set ? [N]
This keyword is asked only when the set you want to
create already exists.
If you do not want to delete this set, you are asked
to give another set to create.

INSTRUME= Give type of instrument.
This item will be put in the header and will determine
the coordinate system

CTYPE1= Enter axis name of first axis [stop axis input]
For the n_th axis the keyword will be CTYPEn=, like
all the following keywords

NAXIS1= Size of axis in grids.

CRPIX1= Reference pixel of the axis.

CUNIT1= Physical units of axis [depends on CTYPE]

CRVAL1= Value at reference pixel in CUNITs.

CDELT1= Grid separation in CUNISs.

CROTA1= Rotation angle of axis in degrees [0.0].
This keyword is only asked in case of a DEC axis.

DUNIT1= Secondary units of axis [depends on CTYPE]
This keyword is only asked in case of a FREQ axis.

DRVAL1= Secondary reference value in DUNITs.
This keyword is only asked in case of a FREQ axis.

FREQ0= Give rest frequency in Hz.
This keyword is only asked in case of a FREQ axis.

BUNIT= Give data units: [W.U.]

FUNCTION= F(RA,...)= [empty]
Give an expression using the syntax in the
description. The number of parameters cannot
exceed the number of created axes. The names of
a parameter is the name of an axes. FUNCTION=
will prompt you with all available parameter names.
If carriage return is pressed, the image will be an
empty set.

Description: Create a set from scratch and fill it with values.
The values are calculated from a user given
expression. The indices of the parameters in that
expression correspond to the indices of the created
axes of the set and each grid is a parameter value.
Illegal operations, like dividing by zero or the
logarithm of a negative value, will cause the result
to be set to BLANK.
For complicated functions the user is advised to
make use of 'recall' files for easy input of the
function definition.

Available mathematics:

1) functions; syntax ff(..); where ff is one of the
following available functions:
abs(x) absolute value of x
sqrt(x) square root of x
sin(x) sine of x
asin(x) inverse sine of x
cos(x) cosine of x
acos(x) inverse cosine of x
tan(x) tangent of x
atan(x) inverse tan of x
atan2(x,y) inverse tan (mod 2pi) x = sin, y = cos
exp(x) exponential of x
ln(x) natural log of x
log(x) log (base 10) of x
sinh(x) hyperbolic sine of x
cosh(x) hyperbolic cosine of x
tanh(x) hyperbolic tangent of x
rad(x) convert x to radians
deg(x) convert x to degrees
erf(x) error function of x
erfc(x) 1-error function
max(x,y) maximum of x and y
min(x,y) minimum of x and y
sinc(x) sin(x)/x (sinc function)
sign(x) sign of x (-1,0,1)
mod(x,y) gives remainder of x/y
int(x) truncates to integer
nint(x) nearest integer
ranu(x,y) generates uniform noise between x and y
rang(x,y) generates gaussian noise with mean x
and dispersion y
ranp(x) generates poisson noise with mean x
ifeq(x,y,a,b) returns a if x == y, else b
ifne(x,y,a,b) returns a if x != y, else b
ifgt(x,y,a,b) returns a if x > y, else b
ifge(x,y,a,b) returns a if x >= y, else b
iflt(x,y,a,b) returns a if x < y, else b
ifle(x,y,a,b) returns a if x <= y, else b
ifblank(x,a,b) returns a if x == BLANK, else b
2) constants; syntax cc; where cc is one of the following
available constants:
PI 3.14159....
C speed of light (SI)
H Planck (SI)
K Boltzmann (SI)
G gravitation (SI)
S Stefan-Boltzman (SI)
M mass of sun (SI)
P parsec (SI)
BLANK Universal undefined value
Note: the Hubble constant is not included.
3) operators; syntax op; where op is one of the following
available operators:
+ addition
- subtraction
* multiplication
/ division
** power
4) parameters; syntax axisname; (CTYPEn=), max 32 names.

Updates: Jul 5, 1990: KGB, document created.
Jul 24, 1990: VOG, function evaluation.
Nov 14, 1991: VOG, $n replaced by axis name.
Oct 20, 1994: KGB, declared USERCHAR and FIEPAR.
Apr 2, 1998: VOG, Use usertext for instrument name