- Form:MN source [NOBL] [BOX=b] [NOZERO] [MASK]
[PIX=p] [SILENT] [W=w1,w2]
-
- source
- the image or spectrum for which the mean
is to be computed
- NOBL
- ignore baseline (last) column in an image
- BOX=b
- find the mean in box b
- NOZERO
- ignore pixels with value zero
- MASK
- ignore masked pixels
- PIX=p
- use every p'th pixel (for speed)
- W=w1,w2
- find the mean in a wavelength calibrated
spectrum in the interval from wavelength w1 to w2.
- SILENT
- do not print the results of the calculation.
The mean of all the pixels in the image contained in buffer 'source' is
computed. Use MASK or NOZERO to ignore masked or zero-valued pixels in the
computation. PIX=p computes the mean using every p'th pixel in every p'th
row, for speed.
The computed mean value is printed at the terminal (unless the SILENT word
is given) and is also loaded into the VISTA variable Mn, where 'n' is the
image buffer number. (ex: the command MN 1 loads the variable M1. The
command MN 31 loads the variable MN31). The value of the mean is also
loaded into the variable MEAN.
The mean is used by other commands such as the TV command for a default
display range, or the DIVIDE command for rescaling images after flat-field
divisions.
See MASK for the operation of the pixel mask.
Examples:
- MN 4
- finds the mean of buffer 4. The
value of the mean is printed on the terminal and is loaded into the
variables MEAN and M4.
- MN 2 PIX=5
- computes the mean using every 5th
pixel in every 5th row. This makes the computation go very fast.
- MN 5 W=4000,5000
- finds the mean of the wavelength-
calibrated spectrum in buffer 5 in the interval from 4000 to 5000 Angstroms.
- MN $Q MASK
- finds the mean of the object in buffer
Q (Q a variable), ignoring masked pixels.
- MN 4 BOX=6
- finds the mean of the object in
buffer 4 using those pixels in box 6.