bracket: bracket bounds a value on the x-axis and y-axis

In MQMF: Modelling and Quantitative Methods in Fisheries

bracket bounds a value on the x-axis and y-axis

Description

bracket scans through a series of predicted values for the location of a target value of the y-axis and returns the two y values that bracket the target, perhaps finding the values closest to 0.5 in a vector between 0 and 1. It also returns the x-axis values that gave rise to the two values bracketing the target, and finally returns the target. For example, imagine generating the proportion mature for a given length of fish using an equation for which there was no analytical solution to what the value of the L50 or the inter-quartile distance was. Bracket can find the two lengths that generate proportions just below 0.5 and just above. It does not matter if, by chance, the target is one of those y-axis values.

Usage

bracket(x, yaxis, xaxis)

Arguments

x	the target predicted value of interest
yaxis	the predicted values reflecting the xaxis values
xaxis	the series of values used to generate the predicted values

Value

a vector of 5 values, left, right, bottom, top and target

See Also

linter

Examples

 L = seq(60,160,1)
 p=c(a=0.075,b=0.075,c=1.0,alpha=100)
 asym <- srug(p=p,sizeage=L) # Schnute and Richards unified growth curve
 L25 <- linter(bracket(0.25,asym,L)) 
 L50 <- linter(bracket(0.5,asym,L)) 
 L75 <- linter(bracket(0.75,asym,L)) 
 ans <- c(L25,L50,L75,L50-L25,L75-L50)
 {cat("   L25    L50      L75   L50-L25 L75-L50 \n")
 cat(round(ans,4),"\n")} 

MQMF documentation built on Sept. 8, 2023, 5:14 p.m.