diff --git a/doc/source/catalog_generation.rst b/doc/source/catalog_generation.rst index 0c940c76a..d5dcbfaaa 100644 --- a/doc/source/catalog_generation.rst +++ b/doc/source/catalog_generation.rst @@ -871,3 +871,32 @@ in the .ecsv: | Theta | THETA_IMAGE | Angle between semi-major and NAXIS1 axes | radians | +----------------+------------------+---------------------------------------------+---------------+ +6: Reading The Output Catalog Files +=================================== +All of the Point and Segmentation catalogs, filter and total, are Enhanced Character-Separated Values (ECSV) +files which are human-readable ASCII tables. As such, it is straight-foward to access the astronomical +source data contained in the rows of the files in a programmatic way via Astropy or Pandas. + +An Astropy example with a Segmentation filter catalog will generate the following Astropy table (abridged view):: + + >>> from astropy.table import Table + >>> astro_tab=Table.read("hst_15064_11_acs_wfc_f814w_jdjb11_segment-cat.ecsv", format="ascii.ecsv") + >>> astro_tab + + X-Centroid Y-Centroid RA DEC ID CI ... CYY CXY Elongation Ellipticity Theta + pix pix deg deg mag(AB) ... 1 / pix2 1 / pix2 rad + float64 float64 float64 float64 int64 float64 ... float64 float64 float64 float64 float64 + ---------- ---------- ------------- ------------- ------- ------- ... --------- --------- ---------- ----------- -------- + 3774.045 87.935 313.5799763 -0.1839533 1 2.144 ... 0.25651 -0.13623 1.30 0.23 52.349 + 3630.189 101.246 313.5819743 -0.1837685 2 1.642 ... 0.12165 -0.00195 1.03 0.03 82.412 + +The “comment" parameter in this Pandas example is necessary so that the reader will skip over the header lines which it cannot +parse. The first line which is actually read is the “line 0" (header=0) which consists of the ascii column names. The result is a +Pandas dataframe for this example of the Point filter catalog:: + + >>> import pandas + >>> df=pandas.read_csv("hst_15064_11_acs_wfc_f814w_jdjb11_point-cat.ecsv", sep=" ", header=0, comment="#") + >>> df + X-Center Y-Center RA DEC ID ... MSkyAp2 StdevAp2 FluxAp2 CI Flags + 0 3774.738972 89.759486 313.579967 -0.183928 1 ... 0.165745 0.009700 4.732320 1.561092 1 + 1 3630.522602 102.347181 313.581970 -0.183753 2 ... 0.151377 0.227345 834.948972 1.189462 4