gmtconvert − Converts, Pastes, and/or Extracts columns from ASCII and binary 1-D tables


gmtconvert [ inputfiles ] [ −A ] [ −D[template] ] [ −E[f|l] ] [ −Fcols ] [ −H[i][nrec] ] [ −L ] [ −I ] [ −N ] [ −S[~]"search string" ] [ −V ] [ −:[i|o] ] [ −b[i|o][s|S|d|D[ncol]|c[var1/...]] ] [ −f[i|o]colinfo ] [ −g[a]x|y|d|X|Y|D|[col]z[+|-]gap[u] ] [ −m[i|o][flag] ]


gmtconvert reads its standard input [or inputfiles] and writes out the desired information to standard output. It can do a combination of three things: (1) convert between binary and ASCII data tables, (2) paste corresponding records from multiple files into a single file, (3) extract a subset of the columns, (4) only extract segments whose header matches a text pattern search, (5) just list all multisegment headers and no data records, and (6) extract first and last data record for each segment. Input (and hence output) may have multiple subheaders if −m is selected, and ASCII tables may have regular headers as well.

ASCII (or binary, see −bi) file(s) holding a number of data columns.



The records from the input files should be pasted horizontally, not appended vertically. [Default processes one file at the time]. Note for binary input, all the files you want to paste must have the same number of columns (as set with −bi).


For multiple segment data, dump each segment to a separate output file [Default writes a multiple segment file to stdout]. Append a format template for the individual file names; this template must contain a C format specifier that can format an integer argument (the segment number); this is usually %d but could be %8.8d which gives leading zeros, etc. [Default is gmtconvert_segment_%d.d].


Only extract the first and last record for each segment of interest [Default extracts all records]. Optionally, append f or l to only extract the first or last record of each segment, respectively.


Give a comma-separated list of desired columns or ranges (0 is first column) [Default outputs all columns].


Input file(s) has header record(s). If used, the default number of header records is N_HEADER_RECS. Use −Hi if only input data should have header records [Default will write out header records if the input data have them]. Blank lines and lines starting with # are always skipped.


Invert the order of rows, i.e., output the final records in reverse order, starting with the last and ending up with the first input row [Default goes forward].


Only output a listing of all multisegment header records and no data records (requires −m and ASCII data).


Do not write records that only contain NaNs in every field [Default writes all records].


Only output those segments whose header record contains the specified text string. To reverse the search, i.e., to output segments whose headers do not contain the specified pattern, use −S~. Should your pattern happen to start with ~ you need to escape this character with a backslash  [Default output all segments].


Selects verbose mode, which will send progress reports to stderr [Default runs "silently"].


Toggles between (longitude,latitude) and (latitude,longitude) input and/or output. [Default is (longitude,latitude)]. Append i to select input only or o to select output only. [Default affects both].


Selects binary input. Append s for single precision [Default is d (double)]. Uppercase S or D will force byte-swapping. Optionally, append ncol, the number of columns in your binary input file if it exceeds the columns needed by the program. Or append c if the input file is netCDF. Optionally, append var1/var2/... to specify the variables to be read.


Selects binary output. Append s for single precision [Default is d (double)]. Uppercase S or D will force byte-swapping. Optionally, append ncol, the number of desired columns in your binary output file. [Default is same as input].


Special formatting of input and/or output columns (time or geographical data). Specify i or o to make this apply only to input or output [Default applies to both]. Give one or more columns (or column ranges) separated by commas. Append T (absolute calendar time), t (relative time in chosen TIME_UNIT since TIME_EPOCH), x (longitude), y (latitude), or f (floating point) to each column or column range item. Shorthand −f[i|o]g means −f[i|o]0x,1y (geographic coordinates).


Examine the spacing between consecutive data points in order to impose breaks in the line. Append x|X or y|Y to define a gap when there is a large enough change in the x or y coordinates, respectively, or d|D for distance gaps; use upper case to calculate gaps from projected coordinates. For gap-testing on other columns use [col]z; if col is not prepended the it defaults to 2 (i.e., 3rd column). Append [+|-]gap and optionally a unit u. Regarding optional signs: -ve means previous minus current column value must exceed |gap to be a gap, +ve means current minus previous column value must exceed gap, and no sign means the absolute value of the difference must exceed gap. For geographic data (x|y|d), the unit u may be meter [Default], kilometer, miles, or nautical miles. For projected data (X|Y|D), choose from inch, centimeter, meter, or points [Default unit set by MEASURE_UNIT]. Note: For x|y|z with time data the unit is instead controlled by TIME_UNIT. Repeat the option to specify multiple criteria, of which any can be met to produce a line break. Issue an additional −ga to indicate that all criteria must be met instead.


Multiple segment file(s). Segments are separated by a special record. For ASCII files the first character must be flag [Default is ’>’]. For binary files all fields must be NaN and −b must set the number of output columns explicitly. By default the −m setting applies to both input and output. Use −mi and −mo to give separate settings to input and output.


The ASCII output formats of numerical data are controlled by parameters in your .gmtdefaults4 file. Longitude and latitude are formatted according to OUTPUT_DEGREE_FORMAT, whereas other values are formatted according to D_FORMAT. Be aware that the format in effect can lead to loss of precision in the 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 D_FORMAT setting.


To convert the binary file test.b (single precision) with 4 columns to ASCII:

gmtconvert test.b −bis 4 > test.dat

To convert the multiple segment ASCII table test.d to a double precision binary file:

gmtconvert test.d −m −bo > test.b

You have an ASCII table with 6 columns and you want to plot column 5 versus column 0. Try

gmtconvert table.d −F 5,0 | psxy ...

If the file instead is the binary file results.b which has 9 single-precision values per record, we extract the last column and columns 4-6 and write ASCII with the command

gmtconvert results.b −F 8,4-6 -bi9s | psxy ...

You want to plot the 2nd column of a 2-column file left.d versus the first column of a file right.d:

gmtconvert left.d right.d −A −F 1,2 | psxy ...

To extract all segments in the file big_file.d whose headers contain the string "RIDGE AXIS", try

gmtconvert big_file.d −m −S"RIDGE AXIS" > subset.d


GMT(1), minmax(1)