Task: imstat Purpose: calculate and plot map statistics Categories: map analysis IMSTAT calculates statistics for images. These are the sum, mean, rms, maximum and minimum value of a region. Statistics can be found for profiles or planes, specified using the axes keyword. The data can be converted to Kelvin, by using 'options=tb' and the beam keyword. Output can be written to the terminal, a log file, or a plot. The options keyword gives control over the plot. The plot header can be suppressed by using options=noheader. An alternative title can be put on the plot by options=title. A useful combination is 'options=noh,ti,title', to get only the string 'title', instead of the full header. Key: in Standard keyword in. See the help on in for more information. Key: region Standard keyword region. See the help on region for more information. Key: axes One axis (for profiles) or two axes (for planes) for which statistics are to be calculated. E.g. 'axes=spectral' computes statistics of each spectrum in the selected region - whether expressed as frequency, velocity, etc. 'axes=longitude,latitude' would compute statistics for each celestial image plane in the dataset (regardless of orientation). axes is case insensitive, and may be specified explicitly by coordinate type (ctype), as listed by PRTHD. In this it is not necessary to specify the algorithm code, e.g. 'RA' matches both 'RA---NCP' and 'RA---SIN', while 'VOPT' matches 'VOPT-F2W'. Axes may also be specified via their order in the image as 'x', 'y', 'z', 'a', 'b', 'c', and 'd' for axes 1 to 7. The following generic values are also understood: 'longitude' ('lng' or 'long'), 'latitude' (or 'lat'), and 'spectral' ('spc' or 'spec'). The default is 'x,y' if the input is multi-dimensional, otherwise 'x'. Key: plot Selects the statistic to be plotted. Minimal matching is applied. The default is 'rms'. 'sum' Plot the sum 'mean' Plot the mean 'rms' Plot the rms 'rrms' Plot the robust rms (median absolute deviation from median *1.48) 'maximum' Plot the maximum 'minimum' Plot the minimum Key: cutoff Data values below the cutoff are not used for the calculation of statistics. Give one real value. This may be followed by the string ',abs' to get a cutoff in the absolute value of the datavalues, or ',lower' to exclude all values above the cutoff. Default is no cutoff. Key: device Standard keyword device. See the help on device for more information. Key: options Options controlling the characteristics of the plot (minimal matching is done): 'tb' Convert the units to brightness temperature, using the input for the beam keyword 'hanning,#' Hanning smooth the data first over # pixels (must be an odd number) 'boxcar,#' Boxcar smooth the data first over # pixels 'deriv,#' Take the derivative after smoothing. If #=1 a one-sided derivative is taken, for #=2 its two-sided. Useful for Zeeman work. 'noheader' Do not write the header information, just the numbers, producing an ASCII file for a plotting program 'nolist' Do not write the statistics to the screen/logfile 'eformat' Always use format 'e' instead of 'g' to write results 'guaranteespaces' Make sure there is always a space between columns (at the cost of precision) 'xmin,#' Give lower x-value on axis 'xmax,#' Give upper x-value on axis 'ymin,#' Give lower y-value on axis 'ymax,#' Give upper y-value on axis (for these four options the default is autoscaling) 'title,#1,#2,#3' Put the string #1 at x-position #2 and y-position #3, with positions measured in units of the coordinates on the axes. If 'title' is the last option, the title is put in the upper left hand corner. 'style,#' This selects the plot style. #=connect means connect the datapoints #=step means make one-bin wide connected horizontal line segments #=histo means bins are drawn as a horizontal line surrounded by two vertical lines Key: beam If options=tb is used, imstat calculates the sum divided by the sum of the beam to get the flux in the selected area, if the units of the input data are 'per beam'. This is then converted to Kelvin by dividing by 2k/lambda^2 * omega, where omega is found from the beam keyword. If the name of a dataset is given for 'beam', imstat assumes it contains a beampattern and sums the data in a region of the same size as the input region. Else, it assumes that 'beam' gives the major and minor axes of the beam in arcsec and it calculates the sum for a Gaussian beam of that size. If 'beam' is omitted, but 'options=tb' was selected, the beam is found from the header (items bmaj and bmin). If neither is present, no conversion is done. Key: log If specified, output is written to the file given by log= instead of to the terminal. Revision: 1.10, 2015/08/11 06:16:34 UTC

Generated by miriad@atnf.csiro.au on 30 Nov 2018