Xiplot plots flux versus wavelength from a FUSE calibrated spectrum (Fits file)
or ASCII file.
The plotted zone can be selected with the mouse left and right buttons.
Some simple modification to the inputs can be performed (wavelength shift, 
rebin, division by a continuum).

Xiplot can also be used to friendly shift & add FUSE sub-exposures and to
plot the results of Martin Lemoine's Fit Program.

NB:A change to a field is active only if you press the 'ENTER' key on keyboard.




INPUT DATA FILE:

The data to be plotted is selected in the field 'Input Data File'. The filename
can be search by pressing the button 'Search File' and browsing the directories.

The filename is assumed to be a FIT file with columns named 'flux' and 'wave'.
However if the filename has a form '*.d*' like 'data.dat' or 'file.d' then 
the file is supposed to be an ASCII file with wavelength in the first column, 
flux in the second and errors in the third.

Any ASCII file can be used as input to Xiplot whatever his name by using
the Keyword ASCII in the calling sequence (ex: xiplot,ascii='MyAsciiFile')



OUTPUT PS FILE:

The main window content can be plotted into a PostScript file.
The output PostScript file is selected in the field 'Output PS File'. 
The plot is written when the 'PostScript' button is pressed.



OUTPUT ASCII FILE:

The main window content can be written into an ASCII file. 
The name of this ASCII file is selected in the field 'Output Ascii File'. 
The content of this file is defined by the radio buttons below the 'Ascii' 
button; according to the selection, the file columns can be one or several 
items among wavelength, wavelength*1e-4, flux, error, quality flag, fit result
from Martin Lemoine's fit program. 
A short header can also be written at the beginning of the ASCII file.
The ASCII file is written when the 'Ascii' button is pressed.



INFO WINDOW

When moving the mouse in the main window, the info window shows the properties
of the current pixel defined by the cursor position.



SMALL WINDOW OVERVIEW

The small window gives an overview of the full data set which is currently 
plotted.
 !! The plotted region in the main window can be changed by pressing the left 
button and moving the mouse in the small window overview.
This allow to move rapidly within the spectrum.



REBIN 

The Rebin slider allows to rebin the data of the plot.
If the Ascii button is pressed, the REBINNED data are written in the
selected ASCII file.



SHIFT

The Shift slider allows to shift the wavelength scale by a fixed number.
If the Ascii button is pressed, the SHIFTED data are written in the
selected ASCII file.



Ymin, Ymax, Xmin, Xmax

The main window limits can be selected by the sliders Ymin, Ymax, Xmin and 
Xmax. These limits can also be directly entered in the corresponding fields
(do not forget to press the Enter key on keyboard).
Alternatively these limits can be changed with the mouse left and right
buttons (see information on Main Window).



Y FULL RANGE 

The 'Y Full Range' button allows to set the Ymin, Ymax limits according to
the value of the data in the current wavelength range of the plot.
The limits cover the full range of Y value with an additional 20% 
for the upper limit; the lower limit is set below 0.
This action is also executed by default when the wavelength range is set by
the mouse left button or with the Xmin or Xmax sliders.



X FULL RANGE

The 'Y Full Range' button allows to set the Xmin, Xmax limits in order to
cover the full range of wavelengths of the current data.



REPLOT

The 'Replot' button allow to redraw the content of the windows. This is useful,
for instance, when the Xiplot window were covered by other windows and comes
back from background.



PRINT

The 'Print' button allows to send the content of the main window to a printer.
The printer configuration is defined by the user and can be saved in the IDL
".Xpdefaults" file. To configure the printer do the following:
In the PRINT window select a 'Printer Specific' or a 'Generic File'. 
In the last case, the filename is defined by the field 'File Name', and after 
the selection of the Orientation (Portrait or Landscape), the OK button allows
to print into a color PostScript File. 
If a 'Printer Specific' cannot be selected a 'Printer Installation' must be
performed by pressing the 'Install...' button. A new printer can be defined
with 'Add Printer...', a good 'Printer Devices' is often 'Generic PostScript 
Printer'. A port must also be selected, then press 'Add Selected' & 'Dismiss'
in the 'Add Printer' window. The new defined printer must appear in 'Printer
Installation' window. Select the wished printer and press 'Dismiss' in this
'Printer Installation' window. Now a 'Printer Specific' can be selected, this
configuration can be saved by pressing the 'Save' button for further IDL
sessions. After the selection of the Orientation (Portrait or Landscape), 
the OK button allows to print into the selected printer.



POSTSCRIPT

The 'PostScript' button allows to print the content of the main window into
the PostScript file defined in the 'Output PS File' field.
Here, the PostScript file is in black&white. To make a color PostScript File,
the 'PRINT' button should be used.



ASCII

The 'Ascii' button allows to write the content of the main window into the 
ASCII file defined in the 'Output ASCII File' field.
The content of this file is defined by the radio buttons below the 'Ascii' 
button; according to the selection, the file columns can be one or several 
items among wavelength, wavelength*1e-4, flux, error, quality flag, fit result
from Martin Lemoine's fit program. 
A short header can also be written at the beginning of the ASCII file.



OVERPLOT

The 'Overplot' button opens a new window to overplot an additional spectrum.
  
 'Rebin' & 'Shift' can be done as for the main spectrum.

 In addition 'Shift in Pixel' allows to perform a shift in pixel unit of 
 the wavelength scale. The information of this Slider can be used to create 
 a 'Shift & Add' file to co-add different shifted sub-exposures.

 The 'Scale' slider allows to multiply the overplotted spectrum by the 
 selected amount. 
 The maximum position of the 'Scale' slider is set by the field 'Scale Max'.

 The 'Gauss Convol' button performs a convolution of the overplotted spectrum 
 by a gaussian of a given width.

 The 'Divide' button divide the main spectrum by the overplotted spectrum
 The overplotted wavelength are interpolated to the wavelength table of
 the main data before the division: (main_spectrum = main_spectrum / overplot).

 The 'Find Shift' button calculate the best Shift in Pixel to be applied on the
 overplotted spectrum to match the main spectrum. The calculated value can be 
 simply recorded for a further 'Shift & Add' operation by pressing the button
 'Add OverPlot File to Shift File List' in the 'Add Expo' window.

 The 'End' button closes the Overplot window.



ADD EXPO

The 'Add Expo' button opens a window to co-add a set of shifted sub-exposures. 

The list of sub-exposures and shifts to be applied are in a 'Shift File List' 
(*.list) which is a two columns ascii file with the files'names in the 
first column and the shift in pixel in the second column.
The 'Shift File List' can be viewed with the 'show' button and edited with the 
'XEdit' button.
A new line can be written in this file if the OverPlot window is open: 
by pressing the button `Add OverPlot File to Shift File List', the filename 
of the data currently overplotted are added to the 'Shift File List' with the
second column equal to the shift in pixels defined in the OverPlot window.
The overplotted file can be changed to the next or the previous file in a set
of sub-exposures following the FUSE filename convention (press the button 
'Previous/Next Spectrum in OverPlot'). 
Note also that the field 'Shift File List' is automatically filled by a
default filename if the OverPlot window is open. The default filename is
'shift_abccc.list' where a is the detector, b is the segment and ccc is 
'lif' or 'sic'.

Finally a 'shift & co-add' operation is performed by pressing the button
'Execute Shift & Add'. The result is (1) the mean of the flux in the different
files shifted by the specified number of pixels or, (2) if the columns 'COUNTS'
and 'CNTERR' are present, can be calculated by the addition of the photon 
count numbers.

The 'Shift and Add' is done assuming that all the co-added files have the
same wavelength scale. The wavelength scale of the result is the same
as the wavelength scale of the first file in the list. In case of a list
of data with different wavelength scales (for example addition of
SiC and LiF data), a new scale has to be defined. In that case, the button
'Execute Resample Shift & Add' do the same as 'Shift and Add' except that the 
wavelength scale is a new one with a constant bin size. In each bin of the new
scale, the flux is evaluated by the addition of all the corresponding pixels 
in the data list and shifted by the specified amount. 

The result of the 'Shift and Add' procedures is plotted in the main window. 
This result can be saved into an ASCII file with the button 'Ascii' (see above).



PLOT FIT

The 'Plot Fit' button allows to overplot the result of a fit to the data
obtained by Martin Lemoine's OWENS fit program. This needs a table of atomic
data (an ascii file with the wavelength in the first column, the element in 
the second, the atomic mass in the third, the oscillator strength in the
fourth and the spontaneous transition probability in the fifth) and a 'Fit
File' (often named 'minimum') in the format of the OWENS output files.



Find Lines

The 'Find Lines' button allows to plot the positions of expected lines
in the wavelength range [W_Min ; W_max] with an equivalent width larger than
'Eq W Min'. The equivalent width is calculated assuming no saturation, 
an HI column density equal to 'N_HI' and solar abundances (Morton 1991). 
No ionization or excitation correction is applied. The positions are given 
assuming the radial velocity given in the field 'Rad.Vel.' 
The equivalent widths of the H2 lines are calculated assuming an H2
temperature of 'Temp.H2' and a molecular fraction of 'f_H2'.
Two different sets of lines can be plotted, each with its own N_HI, Rad.Vel. 
and J_H2_max.