Chapters:
1: Introduction
2: Simple example
3: Invocation
4: Finer Control
5: X-Y Plots
6: Contour Plots
7: Image Plots
8: Examples
9: Gri Commands
10: Programming
11: Environment
12: Emacs Mode
13: History
14: Installation
15: Gri Bugs
16: Test Suite
17: Gri in Press
18: Acknowledgments
19: License
Indices:
Concepts
Commands
Variables

### 8.12.2: Ignoring columns that are not of interest

Quite often a dataset will have many columns, of which only a couple are of interest to you. Consider for example oceanographic data which has columns storing, in order, these variables: (1) depth in water column, (2) "in situ" temperature, (3) "potential" temperature, (4) salinity, (5) conductivity, (6) density, (7) sigma-theta, (8) sound speed, and (9) oxygen concentration. But you might only be interested in plotting a graph of salinity on the x-axis and depth on the y-axis. Here are several ways to do this:

    open file
    read columns y * * x
    draw curve

where the ``*`' is a place-keeper to indicate to skip that column. For a large number of columns, or as an aesthetic choice, you might prefer to write this a

    open file
    read columns y=1 x=4
    draw curve

Many users would just as soon not bother with this syntax, preferring instead to use system tools with which they are more familiar. So a Gawk user might write

    open "gawk '{print($1, $4)}' file |"
    read columns y x
    draw curve

For more on the Gawk command see see Awk.