Re: Transit Fitting plus referencing software in paper

Posted by karenacollins on Jan 26, 2015; 6:44am
URL: http://astroimagej.170.s1.nabble.com/Transit-Fitting-plus-referencing-software-in-paper-tp199p233.html

Hi David,

Thank you for sending your data to me separately. Hopefully the example
plot and plotcfg files I returned are useful to help understand how to
plot and fit externally generated light curves. For the benefit of
others on the support forum, I will review some of my feedback to you here.

I think the main thing that caused trouble is that the data columns in
the table are not labeled. While it is technically possible to use the
unlabeled default names of col_1, col_2, etc., it makes life a lot
easier in AIJ if you label the columns with names that AIJ uses
internally and handles more gracefully. Standard AIJ column names are
described at Multi-plot_Main->Help->'Data naming convention...'.

The first line in a data file is used to define the labels. Use the
same seperator as used in the data part of the file to separate the
headers. The header line may be started with a hashtag (#) to indicate a
comment line, or can simply start with the data column names. Here is an
example of a data column name line for a comma separated data table:

JD_UTC,rel_flux_T1,rel_flux_err_T1

Tab delimited files are generated by AIJ as output, so <tabs> may be
used in place of the commas in the above line. Spaces may also be used
as column separators. In any case, the same separator used in the data
lines should also be used in the column header line.

A common problem plotting data generated externally is that AIJ only
understands certain column names as time columns and subtracts off the
very large JD base numbers to create a proper plot with readable
numbers. The under the hood problem is that the plots in ImageJ (which
AIJ is based on of course) only handle 32-bit floating point numbers
instead of the 64-bit floating point numbers required to handle the very
large JD numbers. The way around that problem is to subtract off the JD
base and show it in the x-axis label below the plot. AIJ will do that
automatically as long the time column label contains JD or J.D. in the
column name in the first line of the table file.

The second reason to label columns with standard AIJ names is so that an
error column can be associated with its corresponding data column by
simply enabling the "Auto Error" option. However, this can be worked
around if desired by using the "Function" operation "Custom Error" on
the Multi-plot Y-data panel and then manually specifying the appropriate
error column in the Y-operand selector.

Karen