12.1: Overview of Gri Commands

• File manipulation Commands are `open', `close', `skip', `read', and `rewind'.
• Control parameters Various `set' commands control values of parameters, like size of plot, linewidth, font, etc.
• Drawing things Various `draw' commands let you draw data, axes, etc.
• Interaction with user The `query' command gets instructions from the user. The `show' command displays messages to user.
• Control program flow The `if' statement controls optional execution of commands see If Statements. The `while' statement allows loops.
• Directory control The `pwd', `cd' and `ls' commands do the usual unix things.
• Interaction with operating system The `system' command passes instructions to the operating system; the output may be saved into a synonym by using `\syn = system ...'. The `get env' command determines the value of any unix environment variables the system has defined. For more discussion see Operating System.
• Statistics Some very limited capabilities exist; for example, `regress' does linear regression.
• Mathematics Simple mathematical manipulation of column, grid, and image data is provided. Also, wherever Gri expects a number, it will accept a reverse-polish expression; for example, `set x size 10' could also be written `set x size {rpn 20 2 /}'. For details see Mathematics.