The syntax you have you used is not correct. integrate() needs as
first argument a function! see ?integrate for more info.
a possible solution could be:
x - seq(-3, 3, 0.1)
y - exp(x)
##
integral - function(z, a, b, step.){
cc - numeric(n - (b-a)/step.)
f - function(x) exp(x)
for(i in 1:n) cc[i] - integrate(f, lower=a+(i-1)*step.,
upper=a+i*step.)$val
cc
}
integral(y, -3, 3, 0.1)
However, since exp has known integral, you do not need to integrate:
exp(x[-1])-exp(x[seq(1, length(x)-1)]))
I hope it helps.
Best,
Dimitris
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/
http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm
- Original Message -
From: Christoph Scherber [EMAIL PROTECTED]
To: r-help@stat.math.ethz.ch
Sent: Friday, February 04, 2005 1:28 PM
Subject: [R] integration function
Dear R users,
I have tried to write a function which gives the step-wise integral
for an exponential function (moving from -3 to 3 in steps of 0.1,
where the output for every step shall be the integral under the
curve of y against x.
However, something seems to be wrong with this function; can anyone
please help me?
x-seq(-3,3,0.1)
y-exp(x)
integral-function(z,a,b,step){
for(i in (1:((b-a)/step))){
c-0
c[i]-integrate(z,lower=a+(i-1)*step,upper=a+i*step)
print(c$integral)
}}
integral(y,-3,3,0.1)
Best regards
Christoph
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