National Aeronautics and Space Administration

Making Histogram

Making a 1D or 2D histogram from a table:

TLMIN and TLMAX are the keywords usually used in an event file and are critical to making correct histograms. "Data Min" and "Data Max" are minimum and maximum values of the selected column and are dynamically calculated.

One needs to supply Min, Max, Bin Sizes for both X and Y column (for 2D histogram, X only for 1D histogram). By default, TLMin and TLMax values are used for Min and Max.

One can select a range of rows in the table for making histogram by providing a "Row Range".

Or one can use selected rows in the table window for making histogram by checking "Use selected rows" checkbox.

"Make" button does the following procedures:

• Create the histogram and save it in a temporary file as an image.
• Write CTYPEn, CRPIXn, CRVALn, and CDELTn keywords to the image, for use in plotting the image with original axes.
• Summary of the temporary file is then opened automatically.

1D histogram:

By selecting only the X column and/or Weight column, one can make a 1D histogram.

Note:

To retain the histogram, one must Save the file before closing it. fv will warn the user of this if the file has not been saved when closing it or exitting the program.