1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
|
<HTML>
<HEAD>
<TITLE>blockmedian</TITLE>
</HEAD>
<BODY>
<H1>blockmedian</H1>
<HR>
<PRE>
<!-- Manpage converted by man2html 3.0.1 -->
blockmedian - filter to block average (x,y,z) data by L1
norm.
</PRE>
<H2>SYNOPSIS</H2><PRE>
<B>blockmedian</B> [ <I>xyz[w]file(s)</I> ] <B>-I</B><I>x</I><B>_</B><I>inc</I>[<B>m|c</B>][/<I>y</I><B>_</B><I>inc</I>[<B>m|c</B>]]
<B>-R</B><I>west/east/south/north</I>[<B>r</B>] [ <B>-C</B> ] [ <B>-F</B> ] [ <B>-H</B>[<I>nrec</I>] ] [ <B>-L</B>
] [ <B>-Q</B> ] [ <B>-V</B> ] [ <B>-W</B>[<B>io</B>] ] [ <B>-:</B> ] [ <B>-bi</B>[<B>s</B>][<I>n</I>] ] [ <B>-bo</B>[<B>s</B>] ]
</PRE>
<H2>DESCRIPTION</H2><PRE>
<B>blockmedian</B> reads arbitrarily located (x,y,z) triples [or
optionally weighted quadruples (x,y,z,w)] from standard
input [or <I>xyz[w]file(s)</I>] and writes to standard output a
median position and value for every non-empty block in a
grid region defined by the <B>-R</B> and <B>-I</B> arguments. Either
<B><A HREF="blockmean.html">blockmean</A></B>, <B>blockmedian</B>, or <B><A HREF="blockmode.html">blockmode</A></B> should be used as a
pre-processor before running <B><A HREF="surface.html">surface</A></B> to avoid aliasing
short wavelengths. These routines are also generally use
ful for decimating or averaging (x,y,z) data. You can mod
ify the precision of the output format by editing the
D_FORMAT parameter in your .gmtdefaults file, or you may
choose binary input and/or output using single or double
precision storage.
<I>xyz[w]file(s)</I>
3 [or 4] column ASCII file(s) [or binary, see <B>-b</B>]
holding (x,y,z[,w]) data values. [w] is an optional
weight for the data. If no file is specified,
<B>blockmedian</B> will read from standard input.
<B>-I</B> <I>x</I><B>_</B><I>inc</I> [and optionally <I>y</I><B>_</B><I>inc</I>] is the grid spacing.
Append <B>m</B> to indicate minutes or <B>c</B> to indicate sec
onds.
<B>-R</B> <I>west,</I> <I>east,</I> <I>south,</I> and <I>north</I> specify the Region of
interest. To specify boundaries in degrees and min
utes [and seconds], use the dd:mm[:ss] format.
Append <B>r</B> if lower left and upper right map coordi
nates are given instead of wesn.
</PRE>
<H2>OPTIONS</H2><PRE>
<B>-C</B> Use the center of the block as the output location
[Default uses the median location (but see <B>-Q</B>)].
<B>-C</B> overrides <B>-Q</B>.
<B>-F</B> Block centers have pixel registration. [Default:
grid registration.] (Registrations are defined in
GMT Cookbook Appendix B on grid file formats.) Each
block is the locus of points nearest the grid value
location. For example, with <B>-R</B>10/15/10/15 and and
<B>-I</B>1: with the <B>-F</B> option 10 <= (x,y) < 11 is one of
25 blocks; without it 9.5 <= (x,y) < 10.5 is one of
36 blocks.
header records can be changed by editing your .gmt
defaults file. If used, <B><A HREF="GMT.html">GMT</A></B> default is 1 header
record. Not used with binary data.
<B>-L</B> Indicates that the x column contains longitudes,
which may differ from the region in <B>-R</B> by [multi
ples of] 360 degrees [Default assumes no periodic
ity].
<B>-Q</B> (Quicker) Finds median z and (x, y) at that z
[Default finds median x, median y, median z].
<B>-V</B> Selects verbose mode, which will send progress
reports to stderr [Default runs "silently"].
<B>-W</B> Weighted modifier[s]. Unweighted input and output
has 3 columns x,y,z; Weighted i/o has 4 columns
x,y,z,w. Weights can be used in input to construct
weighted median values in blocks. Weight sums can
be reported in output for later combining several
runs, etc. Use <B>-W</B> for weighted i/o, <B>-Wi</B> for
weighted input only, <B>-Wo</B> for weighted output only.
[Default uses unweighted i/o]
<B>-:</B> Toggles between (longitude,latitude) and (lati
tude,longitude) input/output. [Default is (longi
tude,latitude)]. Applies to geographic coordinates
only.
<B>-bi</B> Selects binary input. Append <B>s</B> for single precision
[Default is double]. Append <I>n</I> for the number of
columns in the binary file(s). [Default is 3 (or 4
if <B>-W</B> is set) columns].
<B>-bo</B> Selects binary output. Append <B>s</B> for single preci
sion [Default is double].
</PRE>
<H2>EXAMPLES</H2><PRE>
To find 5 by 5 minute block medians from the double preci
sion binary data in hawaii_b.xyg and output an ASCII
table, try
blockmedian hawaii_b.xyg <B>-R</B>198/208/18/25 <B>-I</B>5<B>m</B> <B>-bi</B>3 >
hawaii_5x5.xyg
</PRE>
<H2>SEE ALSO</H2><PRE>
<I><A HREF="blockmean.html">blockmean</A></I>(l), <I><A HREF="blockmode.html">blockmode</A></I>(l), <I>gmt</I>(l), <I><A HREF="gmtdefaults.html">gmtdefaults</A></I>(l),
<I><A HREF="nearneighbor.html">nearneighbor</A></I>(l), <I><A HREF="surface.html">surface</A></I>(l), <I><A HREF="triangulate.html">triangulate</A></I>(l)
</PRE>
<HR>
<ADDRESS>
Man(1) output converted with
<a href="http://www.oac.uci.edu/indiv/ehood/man2html.html">man2html</a>
</ADDRESS>
</BODY>
</HTML>
<body bgcolor="#ffffff">
|
