NDFCOPY - Copies an NDF (or NDF section) to a new location

Description:

This application copies an NDF  to a new location. By supplying an NDF section  as input it may be used to extract a subset, or to change the size or dimensionality of an NDF. A second NDF may also be supplied to act as a shape template, and hence to define the region of the first NDF which is to be copied.

Any unused space will be eliminated by the copying operation performed by this routine, so it may be used as a way of compressing NDF structures from which components have been deleted. This ability also makes NDFCOPY a useful alternative to SETBOUND in cases where an NDF's size is to be reduced.

Usage:

ndfcopy in out

Parameters:

IN = NDF (Read)

The input NDF (or section) which is to be copied.

LIKE = NDF (Read)

This parameter may be used to supply an NDF to be used as a shape template during the copying operation. If such a template is supplied, then its shape will be used to select a matching section from the input NDF before copying takes place. By default, no template will be used and the shape of the output NDF will therefore match that of the input NDF (or NDF section). [!]

OUT = NDF (Write)

The output NDF data structure.

TITLE = LITERAL (Read)

A title for the output NDF. A null value (the default) will cause the title of the NDF supplied for parameter IN to be used instead. [!]

TRIM = _LOGICAL (Read)

If TRUE, then the number of pixel axes in the output NDF will be reduced if necessary to remove any pixel axes which span only a single pixel. For instance if stokes is a three-dimensional data cube with pixel bounds (1:100,-50:40,1:3), and the parameter IN is given the value "stokes(,,2)", then the dimensionality of the output depends on the setting of TRIM: if TRIM=FALSE the output is three-dimensional with pixel bounds (1:100,-50:40,2:2) and if TRIM=TRUE the output is two-dimensional with pixel bounds (1:100,-50:40). In this example, the third pixel axis spans only a single pixel and is consequently removed if TRIM=TRUE. [FALSE]

TRIMWCS = _LOGICAL (Read)

This parameter is only accessed if parameter TRIM is TRUE. It controls the number of axes in the current WCS co-ordinate Frame  of the output NDF. If TRIMWCS=YES, then the current Frame  in the output NDF will have the same number of axes as there are pixel axes in the output NDF. If this involves removing axes, then the axes to retain are specified by parameter USEAXIS. If TRIMWCS=NO then all axes are retained in the current WCS Frame  of the output NDF. Using the example in the description of the TRIM parameter, if the input NDF stokes has a three-dimensional current WCS Frame with axes (RA,Dec,Stokes) and TRIMWSC=YES, then an axis will be removed from the current Frame to make it 2 dimensional (that is, to match the number of pixel axes remaining after the removal of insignificant pixel axes). The choice of which two axes to retain is controlled by parameter USEAXIS. If, on the other hand, TRIMWCS was set to FALSE, then the output NDF would still have two pixel axes, but the current WCS Frame would retain all three axes from the input NDF. If one or more current-Frame axes are removed, the transformation from the current Frame to pixel Frame may become undefined resulting in some WCS operations being unusable. The inverse of this transformation (from pixel Frame to current Frame) is unchanged however. [TRUE]

USEAXIS = LITERAL (Read)

This parameter is only accessed if TRIM and TRIMWCS are both TRUE and some axes need to be removed from the current WCS Frame of the output NDF. It gives the axes which are to be retained in the current WCS Frame of the output NDF. Each axis can be specified using one of the following options.

• An integer index of an axis within the current Frame of the input NDF (in the range 1 to the number of axes in the current Frame).

• An axis Symbol  string such as "RA" or "VRAD".

• A generic option where "SPEC" requests the spectral axis, "TIME" selects the time axis, "SKYLON" and "SKYLAT" picks the sky longitude and latitude axes respectively. Only those axis domains present are available as options.

The dynamic default selects the axes with the same indices as the pixel axes being copied. The value should be given as a comma-separated list. []

Examples:

ndfcopy infile outfile

Copies the contents of the NDF structure infile to the new structure outfile. Any unused space will be eliminated during the copying operation.

ndfcopy in=data1(3:40,-3:17) out=data2 title="Extracted section"

Copies the section (3:40,-3:17) of the NDF called data1 to a new NDF called data2. The output NDF is assigned the new title "Extracted section", which replaces the title derived from the input NDF.

ndfcopy galaxy newgalaxy like=oldgalaxy

Copies a section of the NDF called galaxy to form a new NDF called newgalaxy. The section which is copied will correspond in shape with the template oldgalaxy. Thus, after the copying operation, both newgalaxy and oldgalaxy will have the same pixel-index bounds.

ndfcopy aa(20$\sim$11,20$\sim$11) bb like=aa

Copies from the NDF section consisting of an 11$\times$11 pixel region of aa centred on pixel (20,20), into a new NDF called bb. The shape of the region copied is made to match the original shape of aa. The effect is to extract the selected square region of pixels into a new NDF of the same shape as the original, setting the surrounding region to the bad-pixel value.

Related Applications

KAPPA: SETBOUND; FIGARO: ISUBSET.

Implementation Status:

If present, an NDF's TITLE, LABEL, UNITS, DATA, VARIANCE, QUALITY, AXIS  WCS, and HISTORY  components are copied by this routine, together with all extensions. The output NDF's title may be modified, if required, by specifying a new value via the TITLE parameter.