gmtinfo - Return information about data tables
gmtinfo [ table ] [
-Aa|f|s ] [ -C ] [
-D[dx[/dy]] ] [
-EL|l|H|hcol ] [
-F[i|d|t] ] [
-I[p|f|s]dx[/dy[/dz...] ] [
-L ] [ -S[x][y] ] [
-Tdz[+ccol] ] [ -V[level] ] [
-bibinary ] [ -dinodata ] [ -eregexp ] [ -fflags
] [ -ggaps ] [ -hheaders ] [ -iflags ] [ -oflags
] [ -r ] [ -:[i|o] ]
Note: No space is allowed between the option flag and the
associated arguments.
gmtinfo reads its standard input [or from files] and finds
the extreme values in each of the columns reported as slash-separated
min/max pairs. It recognizes NaNs and will print warnings if the number of
columns vary from record to record. The pairs can be split into two separate
columns by using the -C option. As another option, gmtinfo can
find the extent of data in the first two columns rounded up and down to the
nearest multiple of the supplied increments given by -I. Such output
will be in the text form -Rw/e/s/n, which can be used directly
on the command line for other modules (hence only dx and dy
are needed). If -C is combined with -I then the output will be
in column form and rounded up/down for as many columns as there are
increments provided in -I. A similar option (-T) will provide
a -Tzmin/zmax/dz string for makecpt.
- table
- One or more ASCII (or binary, see -bi[ncols][type])
data table file(s) holding a number of data columns. If no tables are
given then we read from standard input.
- -Aa|f|s
- Specify how the range should be reported. Choose -Aa for the range
of all files combined, -Af to report the range for each file
separately, and -As to report the range for each segment (in
multisegment files) separately. [Default is -Aa].
- -C
- Report the min/max values per column in separate columns [Default uses
<min/max> format]. When used, users may also use -o to limit
which output columns should be reported [all].
- -D
- Modifies results obtained by -I by shifting the region to better
align with the center of the data. Optionally, append granularity for this
shift [Default performs an exact shift].
- -EL|l|H|hcol
- Returns the record whose column col contains the minimum (l)
or maximum (h) value. Upper case (L|H) works on absolute
value of the data. In case of multiple matches, only the first record is
returned. If col is not specified we default to the last column in
the data.
- -F[i|d|t]
]
- Returns the counts of various records depending on the appended mode:
i returns a single record with the total number of tables,
segments, data records, header records, and overall records. In contrast,
d returns information for each segment in the virtual data set:
tbl_number, seg_number, n_rows, start_rec, stop_rec.
t does the same but honors the input table organization and thus
resets seg_number, start_rec, stop_rec at the start of each new
table.
- -I[p|f|s]dx[/dy[/dz...]
- Report the min/max of the first n columns to the nearest multiple
of the provided increments (separate the n increments by slashes),
and output results in the form -Rw/e/s/n (unless -C
is set). If only one increment is given we also use it for the second
column (for backwards compatibility). To override this behavior, use
-Ipdx. If the input x- and y-coordinates all
have the same phase shift relative to the dx and dy
increments then we use those phase shifts in determining the region, and
you may use -r to switch from gridline-registration to
pixel-registration. For irregular data both phase shifts are set to 0 and
the -r is ignored. Use -Ifdx[/dy] to report an
extended region optimized to give grid dimensions for fastest results in
programs using FFTs. Use -Isdx[/dy] to report an
extended region optimized to give grid dimensions for fastest results in
programs like surface. If dx is given as - then the actual min/max
of the input is given in the -R string.
- -L
- Determines common limits across tables (-Af) or segments
(-As). If used with -I it will round inwards so that the
resulting bounds lie within the actual data domain.
- -S[x][y]
- Add extra space for error bars. Useful together with -I option and
when later plotting with psxy -E. -Sx leaves space for
horizontal error bars using the values in third (2) column. -Sy
leaves space for vertical error bars using the values in fourth (3)
column. -S or -Sxy leaves space for both error bars using
the values in third and fourth (2 and 3) columns.
- -Tdz[+ccol]
- Report the min/max of the first (0'th) column to the nearest multiple of
dz and output this as the string -Tzmin/zmax/dz. To
use another column, append +ccol. Cannot be used together
with -I.
- -:[i|o] (more ...)
- Swap 1st and 2nd column on input and/or output.
- -^ or just -
- Print a short message about the syntax of the command, then exits (NOTE:
on Windows just use -).
- -+ or just +
- Print an extensive usage (help) message, including the explanation of any
module-specific option (but not the GMT common options), then exits.
- -? or no arguments
- Print a complete usage (help) message, including the explanation of all
options, then exits.
The ASCII output formats of numerical data are controlled by
parameters in your gmt.conf file. Longitude and latitude are formatted
according to FORMAT_GEO_OUT, absolute time is under the control of
FORMAT_DATE_OUT and FORMAT_CLOCK_OUT, whereas general floating point values
are formatted according to FORMAT_FLOAT_OUT. Be aware that the format in
effect can lead to loss of precision in ASCII output, which can lead to
various problems downstream. If you find the output is not written with
enough precision, consider switching to binary output (-bo if
available) or specify more decimals using the FORMAT_FLOAT_OUT setting.
To find the extreme values in the file ship_gravity.xygd:
gmt info ship_gravity.xygd
Output should look like
ship_gravity.xygd: N = 6992 <326.125/334.684> <-28.0711/-8.6837> <-47.7/177.6> <0.6/3544.9>
To find the extreme values in the file track.xy to the nearest 5
units but shifted to within 1 unit of the data center, and use this region
to draw a line using psxy, run
gmt psxy `gmt info -I5 -D1 track.xy` track.xy -Jx1 -B5 -P > track.ps
To find the min and max values for each of the first 4 columns,
but rounded to integers, and return the result individually for each data
file, use
gmt info profile_*.txt -C -I1/1/1/1
Given seven profiles with different start and stop positions, we
want to find a range of positions, with increment of 5, that are common to
all the profiles. We use
gmt info profile_[123567].txt -L -I5
The file magprofs.txt contains a number of magnetic profiles
stored as separate data segments. We need to know how many segments there
are and use
gmt info magprofs.txt -Fi
The -I option does not yet work properly with time series
data (e.g., -f0T). Thus, such variable intervals as months and years
are not calculated. Instead, specify your interval in the same units as the
current setting of TIME_UNIT.
2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F.
Wobbe