weyl (version 0.0-7)

print.weyl: Print methods for weyl objects

Description

Printing methods for weyl objects follow those for the spray package, with some additional functionality.

Usage

# S3 method for weyl
print(x, ...)

Value

Returns a weyl object.

Arguments

x

A weyl object

...

Further arguments, currently ignored

Author

Robin K. S. Hankin

Details

Option polyform determines whether the object is to be printed in matrix form or polynomial form: as in the spray package, this option governs dispatch to either print_spray_polyform() or print_spray_matrixform().

> a <- rweyl()
> a    # default print method
A member of the Weyl algebra:
  x  y  z dx dy dz     val
  1  2  2  2  1  0  =    3
  2  2  0  0  1  1  =    2
  0  0  0  1  1  2  =    1
> options(polyform = TRUE)
> a
A member of the Weyl algebra:
+3*x*y^2*z^2*dx^2*dy +2*x^2*y^2*dy*dz +dx*dy*dz^2
> options(polyform = FALSE)  # restore default

Irrespective of the value of polyform, option weylvars controls the variable names. If NULL (the default), then sensible values are used: either [xyz] if the dimension is three or less, or integers. But option weylvars is user-settable:

> options(weylvars=letters[18:20])
> a
A member of the Weyl algebra:
  r  s  t dr ds dt     val
  1  2  2  2  1  0  =    3
  2  2  0  0  1  1  =    2
  0  0  0  1  1  2  =    1
> options(polyform=TRUE)
> a
A member of the Weyl algebra:
+3*r*s^2*t^2*dr^2*ds +2*r^2*s^2*ds*dt +dr*ds*dt^2
> options(polyform=FALSE) ; options(weylvars=NULL)

If the user sets weylvars, the print method tries to do the Right Thing (tm). If set to c("a","b","c"), for example, the generators are named c(" a"," b"," c","da","db","dc") [note the spaces]. If the algebra is univariate, the names will be something like d and x. No checking is performed and if the length is not equal to the dimension, undesirable behaviour may occur. For the love of God, do not use a variable named d. Internally, weylvars works by changing the sprayvars option in the spray package.

Note that, as for spray objects, this option has no algebraic significance: it only affects the print method.

Examples

a <- rweyl()
print(a)
options(polyform=TRUE)
print(a)