Xsample: Generates a random sample of the unknowns for a linear...
In LIM: Linear Inverse Model examples and solution methods

Description Usage Arguments Details Value Author(s) References See Also Examples

Given an inverse input list, randomly samples the unknowns, using an MCMC method

1	Xsample(lim, exact = NULL, ...)

`lim`	a list that contains the linear inverse model specification, as generated by function `setup.limfile`.
`exact`	if not `NULL`, a vector containing the numbers of the equations to be solved exactly; if `NULL`, all equations are considered exact.
`...`	extra parameters passed to function `xsample` from package`limSolve`.

For overdetermined LIM problems, the inverse equations may be split up in equations which have to be exactly met and other equations which have to be approximated.

exact is a vector with the exact equations

The default settings of xsample will often not do. For instance, the default consists of 3000 iterations (iter) and a jump length of jmp of 0.1. You may need to increase one of those to ensure that the entire solution space has been adequately sampled.

a 2-columned vector containing the minimum (column 1) and maximum (column 2) of each unknown.

Karline Soetaert <karline.soetaert@nioz.nl>

Van den Meersche K, Soetaert K, Van Oevelen D (2009). xsample(): An R Function for Sampling Linear Inverse Problems. Journal of Statistical Software, Code Snippets, 30(1), 1-15.

http://www.jstatsoft.org/v30/c01/

Varranges which estimates the ranges of inverse variables

Plotranges to plot the ranges

function xsample from packagelimSolve

# sample solution space
  xs <- Xsample(LIMRigaAutumn, iter = 500, jmp = 5)
  # remove flows that are invariable (sd=0)
  xs <- xs[ ,-which(apply(xs, 2, sd) == 0 )]
  #pairs plot
  pairs(xs, gap = 0, pch = ".", upper.panel = NULL)