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yacas

yacas interface


Description

Interface to the yacas computer algebra system.

Usage

yacas(x, ...)
## S3 method for class 'character'
yacas(x, verbose = FALSE, method, 
    retclass = c("expression", "character", "unquote"), 
    addSemi = TRUE, ...)

Arguments

x

A yacas character string or an R expression without terminating semicolon to be processed by yacas.

...

Additional arguments ultimately passed down to yacas.character.

verbose

A logical value indicating verbosity of output or "input" to only show input to yacas but not output from yacas or "output" to only show output from yacas but not input to yacas.

method

method used to communicate with yacas. If "socket" is specified then the same yacas session is used on a sequence of calls. If "system" is specified then a new instance of yacas is used just for the period of that call. "system" does not require that the system be configured to support telnet/sockets and so may be useful in some instances. If no value is specified the default is taken from getOption("yacas.method") and if that is not specified "socket" is used. "socket" and "system" may be abbreviated.

addSemi

If TRUE a semicolon is added to the character string sent to yacas. This can be set to FALSE if its known that the character string already has a trailing semicolon. It is ignored if retclass="expression".

retclass

The class of the first component of the yacas structure. It defaults to "expression" but may be specified as "character" or "unquote". "unquote" is the same as "character" except that if the character string returned would have otherwise had quotes in the first and and last positions then they are stripped.

Details

The user supplies an R expression, an R function name corresponding to a function with a single line body, a formula or a yacas input string. In the case of a formula it is regarded as an expression represented by the right hand side of the formula while the left hand side, if any, is ignored.

Note the silent version syacas().

Value

An R object of class "yacas" is returned. If PrettyPrinter("OMForm") is in effect, which it is by default, then the first component is an R expression and the OMForm component contains OpenMath XML code. In other cases the first component is NULL and the YacasForm or PrettyForm components have display information.

Generally an expression. Refer to details.

Note

Windows Installation. On Windows one can install Ryacas by issuing the commands:

install.packages("Ryacas", dep = TRUE)
library(Ryacas)
yacasInstall()

or by using the Packages | Install package(s) menu in place of the first command. The second command downloads scripts.dat and yacas.exe from the internet and installs them into R_HOME/library/Ryacas/yacdir where R_HOME is the location of your R installation.

Normally the default locations of yacas, its initialization file and the scripts file are sufficient but, if necessary, they can be overridden via the environment variables: YACAS_HOME, YACAS_INIT and YACAS_SCRIPTS. The YACAS_INVOKE_STRING environment variable discussed in the next section overrides all three of these.

All OS Installation. The YACAS_INVOKE_STRING environment variable can be used to override the invocation string for yacas. Normally it is not used. If it does need to be used then a typical use might be:

library(Ryacas)
# only need to do the file.copy command once
file.copy(system.file("yacdir/R.ys", package = "Ryacas"), "~/.yacsrc")
# this needs to be done once per session
Sys.setenv(YACAS_INVOKE_STRING = "yacas -pc --server 9734")
demo(Ryacas) # test it out

yacmode. There is also a utility yacmode which is called without arguments and just turns R into a terminal into yacas until one quits out of it (and back to R) by entering stop, end, quit, exit or e.

Startup. yacas starts up when yacasStart() is called or the first time yacas is called. yacas is shut down when yacasStop() is called or when the package is detached using the detach() R command. On Windows, when yacas is shut down, the yacas process is terminated on Windows XP Pro but not on other versions of Windows. In those cases there will be a dangling process that the user must terminate manually.

Translation. The translation process occurs in several steps. If the input to the yacas function is an expression then it is translated to a valid yacas character string (otherwise, it is sent to yacas unprocessed). Yacas then processes the string and if retclass="expression" it is translated back to an R expression (otherwise it is sent back unprocessed). Examples of translations are:

R yacas
sin(x) Sin(x)
deriv(sin, x) Deriv(x)Sin(x)
log(x) Ln(x)

References

Examples

yacas(expression(Factor(x^2-1)))
exp1 <- expression(x^2 + 2 * x^2)
exp2 <- expression(2 * exp0)
exp3 <- expression(6 * pi * x)
exp4 <- expression((exp1 * (1 - sin(exp3))) / exp2)
print(yacas(exp4))

print(yacas("Version()")) # yacas version

# see demo("Ryacas-Function")

Ryacas0

Legacy 'Ryacas' (Interface to 'Yacas' Computer Algebra System)

v0.4.3
GPL-2
Authors
Mikkel Meyer Andersen [aut, cre, cph], Rob Goedman [aut, cph], Gabor Grothendieck [aut, cph], Søren Højsgaard [aut, cph], Grzegorz Mazur [aut, cph], Ayal Pinkus [aut, cph], Nemanja Trifunovic [cph] (UTF-8 part of yacas (src/yacas/include/yacas/utf8*))
Initial release

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