Restrict a Numeric Variable to a Positive Value
Restrict a numeric value x to a positive value using a differentiable function.
GT0 stands for “greater than zero”.
GT0(x,eps=1e-4)
x |
vector of values |
eps |
minimum value greater than zero. |
if (x >= eps)..........GT0 = x if (0 < x < eps).......GT0 = (eps/2) * (1 + (x/eps)^2) if (x <= 0)............GT0 = eps/2
Jon T. Schnute, Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo BC
local(envir=.PBSmodEnv,expr={
oldpar = par(no.readonly=TRUE)
plotGT0 <- function(eps=1,x1=-2,x2=10,n=1000,col="black") {
x <- seq(x1,x2,len=n); y <- GT0(x,eps);
lines(x,y,col=col,lwd=2); invisible(list(x=x,y=y)); }
testGT0 <- function(eps=c(7,5,3,1,.1),x1=-2,x2=10,n=1000) {
x <- seq(x1,x2,len=n); y <- x;
plot(x,y,type="l");
mycol <- c("red","blue","green","brown","violet","orange","pink");
for (i in 1:length(eps))
plotGT0(eps=eps[i],x1=x1,x2=x2,n=n,col=mycol[i]);
invisible(); };
testGT0()
par(oldpar)
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