xranges {limSolve} | R Documentation |
Given the linear constraints
Ex=f
Gx>=h
finds the minimum and maximum values of all elements of vector x
by successively minimising and maximising each x
, using linear programming
uses linear programming function lp
from package lpSolve.
xranges(E=NULL, F=NULL, G=NULL, H=NULL, ispos=FALSE, tol=1e-8, central = FALSE, full=FALSE)
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. |
ispos |
if TRUE , it is imposed that unknowns are positive
quantities.
|
tol |
tolerance for equality and inequality constraints. |
central |
if TRUE, the mean value of all range solutions is also outputted. |
full |
if TRUE , all range solutions are also outputted.
|
The ranges are estimated by successively minimising and maximising each unknown, and using linear programming.
by default linear programming assumes that all unknowns are positive.
If this is the case, set ispos
equal to TRUE; the function will
execute faster then. If ispos
is FALSE
, then a system double
the size of the original system must be solved.
xranges
outputs only the minimum and maximum value of each flow unless:
full
is TRUE
. In this case, all the results of the successive
minimisation and maximisation will be outputted, i.e. for each linear
programming application, not just the value of the unknown being optimised
but also the corresponding values of the other unknowns will be outputted.
If central
is TRUE
, then the mean of all the results of the
linear programming will be outputted.
This may be a good starting value for xsample
Note: the columns corresponding to the central
value and the
full
results are valid solutions of the equations Ex=F
and Gx>=H. This is not the case for the first two columns (with
the minimal and maximal values).
a matrix with at least two columns:
column 1 and 2: the minimum and maximum value of each x
if central
is TRUE: column 3 = the central value
if full
is TRUE: next columns contain all valid range solutions
Karline Soetaert <k.soetaert@nioo.knaw.nl>
varranges
, for range estimation of variables,
xsample
, to randomly sample the lsei problem
lp
: linear programming from package lpSolve
# Estimate the ranges in the Diet Composition of Mink A <- rbind(Minkdiet$Prey,rep(1,7)) B <- c(Minkdiet$Mink,1) (DC<-xranges(A,B,ispos=TRUE)) (DC<-xranges(A,B,G=diag(7),H=rep(0,7)))