Hello everybody!
I have problems with integrating my function.
My primary function is a survival function of the following type:
surviv <- exp(-k*x)/(1+exp(alpha*(x-tau)))
I would like to integrate this function over a defined range and obtain a
vector with all the values from integrate(surviv, 0, x) for x <- 1:N.
I unfortunately obtain just a scalar value corresponding to the last
integrated x.
How do I have to proceed if I want to obtain a vector with all the results?
I have tried to solve this problem by adding a while loop. It works but
the expression becomes to complex if I want to perform further optimization.
Have any one a solution for this problem?
Thanks a lot in advance.
Example
# General equation
beta1 <- 0.001
beta2 <- 0
Hct0 <- 0.27
tau <- 70
k <- 0.001
alpha <- 0.3
T2 <-40
step <- function(x){
if(x>=0) step <- 1
else step <- 0
}
Nmax <- 250
n <- 1
while(n<Nmax){
surviv <- function(n){
surviv <- exp(-k*n)/(1+exp(alpha*(n-tau)))
}
geq <- function(n){
geq <-
Hct0+beta1*as.integer(integrate(surviv,0,n)[1])+step(n-T2)*(beta2-beta1)*as.
integer(integrate(surviv,0,n-T2)[1])
}
plot(n, geq(n), type="p", pch=19, xlim=c(0,250),
ylim=c(0.25,0.35), xlab="time in days", ylab="Hct")
par(new=T)
print(c(n, surviv(n), geq(n),
as.integer(integrate(surviv,0,n)[1]))
n <- n + 1
}
Robert M. Kalicki, MD
Department of Nephrology and Hypertension
University of Bern
Abteilung für Nephrologie und Hypertonie (KiKl G5)
Freiburgstrasse 15
CH-3010 Inselspital
Tel: +41316329663
Fax:+41316329734
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