exp4p {berryFunctions} R Documentation

## 4-parametric exponential function

### Description

Fits an exponential function of the form a*e^(b*(x+c))+d

### Usage

exp4p(x, y, digits = 2, plot = FALSE, las = 1, col = 1:6, legarg = NULL, ...)


### Arguments

 x, y x and y Data digits significant digits for rounding R^2. DEFAULT: 2 plot plot data and fitted functions? DEFAULT: FALSE las label axis style, see par. DEFAULT: 1 col 6 colors for lines and legend texts. DEFAULT: 1:6 legarg Arguments passed to legend. DEFAULT: NULL ... further graphical parameters passed to plot

### Details

This is mainly a building block for mReg

### Value

Data.frame with the 4 parameters for each optim method

### Note

Optim can be slow! It refers to the functions rmse and rsquare, also in this package. L-BFGS-B needs finite values. In case it doesn't get any with the initial parameters (as in the first example Dataset), it tries again with the parameters optimized via Nelder Mead.

### Author(s)

Berry Boessenkool, berry-b@gmx.de, 2012-2013, outsourced from mReg in July 2014

mReg, lm

### Examples

## Not run: ## Skip time consuming checks on CRAN
# exponential decline of temperature of a mug of hot chocolate
tfile <- system.file("extdata/Temp.txt", package="berryFunctions")
plot(temp)
temp <- temp[-20,] # missing value - rmse would complain about it
x <- temp$Minuten y <- temp$Temp
rm(tfile, temp)

exp4p(x,y, plot=TRUE)
# y=49*e^(-0.031*(x - 0  )) + 25 correct, judged from the model:
# Temp=T0 - Te *exp(k*t) + Te     with    T0=73.76,  Tend=26.21, k=-0.031
# optmethod="Nelder-Mead"  # y=52*e^(-0.031*(x + 3.4)) + 26 wrong

## End(Not run)



[Package berryFunctions version 1.22.5 Index]