Package noaa.coastwatch.tools

Class cwstats

java.lang.Object
noaa.coastwatch.tools.cwstats
public final class cwstats extends Object

The statistics utility calculates a number of statistics for each variable in an earth data file.

Name

cwstats - calculates earth data file statistics.

Synopsis

cwstats [OPTIONS] input

Options:

-h, --help
-i, --region=LAT/LON/RADIUS
-l, --limit=STARTROW/STARTCOL/ENDROW/ENDCOL
-m, --match=PATTERN
-p, --polygon=FILE
-s, --stride=N
-S, --sample=FACTOR
--version

Description

The statistics utility calculates a number of statistics for each variable in an earth data file:

  • Count - the count of total data values sampled
  • Valid - the number of valid (not missing) data values
  • Min - the minimum data value
  • Max - the maximum data value
  • Mean - the average data value
  • Stdev - the standard deviation from the mean
  • Median - the median data value

To speed up the statistics calculations, a subset of the data values in each variable may be specified using either the --stride or --sample options, and one of the --limit, --region, or --polygon options. The --match option may also be used to limit the statistics calculations to a subset of the variables.

Parameters

Main parameters:

input
The input data file name.

Options:

-h, --help
Prints a brief help message.
-i, --region=LAT/LON/RADIUS
The sampling region for each two-dimensional variable. The region is specified by the center latitude and longitude in degrees, and the radius from the center in kilometers. Only data within the rectangle specified by the center and radius is sampled. By default, all data is sampled. Only one of the --region, --limit, or --polygon options may be specified.
-l, --limit=STARTROW/ENDROW/STARTCOL/ENDCOL
The sampling limits for each two-dimensional variable in image coordinates. Only data between the limits is sampled. By default, all data is sampled. Only one of the --region, --limit, or --polygon options may be specified.
-m, --match=PATTERN
The variable name matching pattern. If specified, the pattern is used as a regular expression to match variable names. Only variables matching the pattern are included in the calculations. By default, no pattern matching is performed and all variables are included.
-p, --polygon=FILE
The file name containing a list of polygon vertex points to use for constraining the statistics calculation. The file must be an ASCII text file containing vertex points as latitude / longitude pairs, one pair per line, with values separated by spaces or tabs. The points are specified in terms of earth location latitude and longitude in the range [-90..90] and [-180..180] with a datum matching that of the input file. Only data inside the polygon is sampled. By default, all data is sampled. Only one of the --region, --limit, or --polygon options may be specified.
-s, --stride=N
The sampling frequency for each variable dimension. The default is to sample all data values (stride = 1).
-S, --sample=FACTOR
The sampling factor for each variable. The sampling factor is a value in the range [0..1] that specifies the number of data values sampled as a fraction of the total number of data values. Optionally, the sample value can be specified in percent, eg: 50%. To sample 1 percent of all data values, the sample factor would be specified as 0.01 or 1%. The default is to sample all data values (factor = 1).
--version
Prints the software version.

Exit status

0 on success, > 0 on failure. Possible causes of errors:

  • Invalid command line option
  • Invalid input file name
  • Unsupported input file format
  • Error reading input data values

Examples

The following shows a statistics calculation on a CoastWatch HDF file from the Great Lakes:

   phollema$ cwstats 2002_197_1719_n16_gr.hdf

   Variable       Count     Valid     Min       Max       Mean       Stdev     
   avhrr_ch1      1048576   483728    3.49      74.36     13.059646  11.371605 
   avhrr_ch2      1048576   483728    1.97      71.35     18.520041  9.844144  
   avhrr_ch3a     1048576   483728    0.53      52.84     14.664213  8.88201   
   avhrr_ch4      1048576   483728    -44.8     31.55     11.052207  13.683309 
   avhrr_ch5      1048576   483728    -45.48    27.05     7.978351   13.185983 
   sst            1048576   483728    -44.51    51.43     20.166333  16.714169 
   cloud          1048576   1048576   0         127       23.24175   37.179013 
   sat_zenith     1048576   483728    0.36      0.7       0.466376   0.077153  
   sun_zenith     1048576   483728    0.87      0.95      0.907019   0.022209  
   rel_azimuth    1048576   483728    -0.58     -0.33     -0.465731  0.058149  
   graphics       1048576   1048576   0         14        6.84576    2.931459
Since:
3.1.0
Author:
Peter Hollemans