Chapters: 1: Introduction 2: Simple example 3: Invocation 4: Finer Control 5: XY 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 
10.8: MathematicsGri lets you do some simple mathematical manipulations on your column and grid data.
10.8.1: Column dataThe column operators are `= ', `+= ', `= ', `*= ',
`/= ', `^= ' (exponentiation) and `_= ' (logarithm). There
must be spaces before and after the operators, but no space between the
2 letters of the operators. The operations may be applied not only to
`x ' and `y ' as shown, but also to `z ' (used to hold data
to be contoured or written as symbols), and `u ' and `v ' (used
to store vector fields).
The axis scales are not changed by mathematical operations on the columns, regardless of whether the scales were set manually or by Gri command (see Axis Scaling).
Elements of columns are available by the ` Examples:
See also see Tertiary Operators for a method of assigning or altering column data using the RPN operator.
10.8.2: Grid dataVarious commands let you alter grid data as used in contouring (see Contour Plots). Possible commands are as follows.
10.8.2.1: Image dataVarious commands let you alter image data (see Images.). Possible commands are as follows.
10.8.2.2: Image grayscale/colorscaleVarious commands let you alter image data (see Images). Possible commands are as follows.
10.8.2.3: VariablesPossible commands are:
