varranges: Calculates ranges of inverse variables in a linear inverse...

In limSolve: Solving Linear Inverse Models

Description

Given the linear constraints

Ex=f

Gx>=h

and a set of "variables" described by the linear equations

Var = EqA.x+EqB

finds the minimum and maximum values of the variables by successively minimising and maximising each variable equation

Usage

varranges(E=NULL, F=NULL, G=NULL, H=NULL, EqA, EqB=NULL, 
  ispos=FALSE, tol=1e-8)

Arguments

E	numeric matrix containing the coefficients of the equalities Ex=F.
F	numeric vector containing the right-hand side of the equalities.
G	numeric matrix containing the coefficients of the inequalities Gx>=H.
H	numeric vector containing the right-hand side of the inequalities.
EqA	numeric matrix containing the coefficients that define the variable equations.
EqB	numeric vector containing the right-hand side of the variable equations.
ispos	if TRUE, it is imposed that unknowns are positive quantities.
tol	tolerance for equality and inequality constraints.

Value

a 2-column matrix with the minimum and maximum value of each equation (variable)

Note

uses linear programming function lp from package lpSolve.

Author(s)

Karline Soetaert <[e-mail]>

References

Michel Berkelaar and others (2010). lpSolve: Interface to Lp_solve v. 5.5 to solve linear/integer programs. R package version 5.6.5. http://CRAN.R-project.org/package=lpSolve

See Also

Minkdiet, for a description of the Mink diet example.

xranges, to estimate ranges of inverse unknowns.

xsample, to randomly sample the lsei problem

lp: linear programming function from package lpSolve.

Examples

# Ranges in the contribution of food 3+4+5 in the diet of Mink (try ?Minkdiet)

E     <- rbind(Minkdiet$Prey, rep(1, 7))
F     <- c(Minkdiet$Mink, 1)
EqA   <- c(0, 0, 1, 1, 1, 0, 0)                    # sum of food 3,4,5
(isoA <- varranges(E, F, EqA = EqA, ispos = TRUE)) # ranges of part of food 3+4+5

# The same, but explicitly imposing positivity
varranges(E, F, EqA = EqA, G = diag(7), H = rep(0, 7)) 

Example output

           min       max
[1,] 0.2090234 0.4752937
           min       max
[1,] 0.2090234 0.4752937

limSolve documentation built on Nov. 12, 2019, 3 p.m.