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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
 		index.html#Top Programming.html#Programming Gri: Loops Gri: Reverse Polish Mathematics index.html#Top Gri: Reverse Polish Mathematics

10.8: Mathematics

Gri lets you do some simple mathematical manipulations on your column and grid data.

10.8.1: Column data

The 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 `@' reverse polish operator (see rpn Mathematics).

Examples:

  • To multiply all the x data by 10, use `x *= 10'; to add 5 to each y-value, use `y += 5'.
  • To set all the y data to 10, do `y = 10'. (This will only work if you've already read column data.)

See also see Tertiary Operators for a method of assigning or altering column data using the RPN operator.

10.8.2: Grid data

Various commands let you alter grid data as used in contouring (see Contour Plots). Possible commands are as follows. 


grid data = number
grid data += number
grid data -= number
grid data *= number
grid data /= number
grid data ^= number # take data to power 'number'
grid data _= number # take log base 'number'
grid x = number
grid x += number
#... others as in `grid data'
grid y = number
grid y += number
#... others as in `grid data'

10.8.2.1: Image data

Various commands let you alter image data (see Images.). Possible commands are as follows. 


image += number
image -= number
image *= number
image /= number
image ^= number # power
image _= number # logarithm

10.8.2.2: Image grayscale/colorscale

Various commands let you alter image data (see Images). Possible commands are as follows. 


image grayscale += number
image grayscale  -= number
image grayscale  *= number
image grayscale  /= number
image grayscale  ^= number # power
image grayscale  _= number # logarithm
image colorscale += number
image colorscale  -= number
image colorscale  *= number
image colorscale  /= number
image colorscale  ^= number # power
image colorscale  _= number # logarithm

10.8.2.3: Variables

Possible commands are: 


.variable. = number
.variable. += number
.variable. -= number
.variable. *= number
.variable. /= number
.variable. ^= number # power
.variable. _= number # logarithm

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