plotGS

Description

plotGS is a specialized plotting utility designed to visualize grain size distribution data. It reads ASCII files containing grain size percentages (typically from laboratory analysis) and plots them as a bar graph or histogram. The tool can handle different input formats, including a custom format (likely from DelayEditor output) and data from the Pacific Geoscience Centre (PGC).

This tool is useful for rapidly visualizing sedimentological data, allowing for quick comparison of different samples or characterization of sediment types.

Usage 

plotGS <infile(s)> [-outfile <filename.meta>] [-size <dx> <dy>] [-yrange <min> <max>] [-pgc] [-v]

Arguments

Option Description  
<infile(s)> Required. One or more input ASCII files containing grain size data.  
-outfile <filename.meta> Specifies the output PostScript metafile name. plot.meta
-size <dx> <dy> Specifies the plot size in centimeters. 15.0 15.0
-yrange <min> <max> Sets the Y-axis range (percentage). 0.0 to 40.0
-pgc Indicates that the input file is in PGC (Pacific Geoscience Centre) format. This implies a different parsing and plotting approach, including extraction of mean, standard deviation, kurtosis, and skewness, and plotting against Phi units.  
-v Enable verbose output.  
-sparse (Present in USAGE but not implemented) Intended for sparse plotting.  

Input File Formats

  • Default (likely from DelayEditor output): Contains a series of percentage values for predefined grain size bins (e.g., 25000um, 19000um down to 75um, and mud/pan).
  • PGC (-pgc) format: A more complex ASCII format that includes metadata like sample number, latitude, longitude, and then a list of Phi units and corresponding relative and cumulative percentages.

How It Works

  1. Initialization: Parses command-line arguments to set plotting options, input file formats (pgc_flag), plot size, and ranges.
  2. File Reading Loop: Loops through each input file specified:
    • Opens the input ASCII file.
    • Data Loading:
      • If pgc_flag is set: It parses the multi-line PGC format, extracting sample number, latitude, longitude, and then Phi values and percentages. It also calculates mode, mean, stdev, kurt, skew from the Phi data. It opens .llz and .lln files for writing coordinate and number data.
      • If pgc_flag is not set: It reads a predefined sequence of percentage values for different grain size bins.
    • Plotting: Calls do_plot() to generate the plot.
    • Closes the input file.
  3. do_plot() Function:
    • Draws the main plot border.
    • Sets X-axis range (from 0.0 to fractions or Phi units if pgc_flag is set) and Y-axis range (percentage).
    • PGC Specific Plotting: If pgc_flag is set:
      • Draws vertical lines to delineate gravel, sand, silt, and clay boundaries in Phi units.
      • Displays sample number, skewness, kurtosis, mean, mode, and standard deviation on the plot.
      • Plots bars representing perc_gs[j] (percentages) against phi[j] (Phi units).
    • Default Plotting: Plots bars representing percentages for each predefined grain size bin.
    • Adds general plot title and labels.
  4. Cleanup: Calls plot_close to finalize the PostScript output.

Output Files

  • <outfile_name>: A PostScript metafile (.meta) containing a bar graph or histogram of grain size distribution.
  • <infile_prefix>.llz: ASCII file containing latitude, longitude, mean, standard deviation for each sample (if -pgc is used).
  • <infile_prefix>.lln: ASCII file containing latitude, longitude, sample number (if -pgc is used).

Dependencies

  • plotlib.h: For plotlib functions.
  • support.h: For general utility functions.
  • math.h: For mathematical functions.

Notes

plotGS is a useful tool for sedimentologists to quickly visualize and compare grain size data from multiple samples. The PGC format support highlights its use with specific scientific datasets. The tool creates a PostScript output, which is suitable for inclusion in reports and presentations. The -sparse option is listed but not implemented.