File:SQRTDiffusion.png

Uploaded by Thire
Upload date 2005-12-21T21:55:05Z
MIME type image/png
Dimensions 1200 × 900 px
File size 17.0 KB
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Description

three sample paths of an square root diffuion process (Cox Ingersoll Ross), see SDE in the image

Deutsch: Drei Pfade von Wurzel-Diffusionsprozessen
Date 2 May 2012-20
Source made with the free software R, see the source code at the bottom
Author Thomas Steiner
Permission
(Reusing this file)
Thomas Steiner put it under the GFDL

Licensing

GNU head Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License.
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attribution share alike
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This licensing tag was added to this file as part of the GFDL licensing update.

R-Quelltext:

##SQRT-Diffusion mit normalverteiltem Anfangswert
sdiff<-function(kappa=1, theta=1.2, sigma=0.2, init=c(0, 1), from=0, to=2, steps=500*(to-from)) {
  t<-seq(from,to,length=steps)
  cir<-rnorm(n=1,mean=init[1],sd=sqrt(init[2]))
  for (i in (1:(steps-1))) {
    cir[i+1]=cir[i] + kappa*(theta-cir[i])*(to-from)/steps + sqrt(cir[i])*sigma*rnorm(n=1,mean=0,sd=sqrt((to-from)/steps))
  }
  return(cir)
}

cols=c("navy", "darkolivegreen4", "red")
t<-seq(0,2,length=1000)
set.seed(17091945) 

png(filename="SQRTDiffusion.png", width=1200, height=900, pointsize=12)
par(bg="lightgrey")
matplot(t,sdiff(init=c(0,0)),type="l", xlab="", ylab="",col=cols[1], lwd=2, ylim=c(0,1.55))
lines(t,sdiff(init=c(1.5,0)),col=cols[2], lwd=2)
lines(t,sdiff(),col=cols[3], lwd=2)
title(main="SQRT - Diffusion", cex.main=2.5)
text(x=1.85,y=0,expression(list(kappa==1, theta==1.2, sigma == 0.2)) )
text(x=1.4,y=0.3,expression(paste("d",X[t]==kappa(theta-X[t]),"dt+",sigma,sqrt(X[t]),"d",  W[t])),cex=2.5)
text(x=0,y=0.07, expression(X[0]==0),col=cols[1])
text(x=0,y=1.42, expression(X[0]==2),col=cols[2])
text(x=0.03,y=0.35, expression(paste(X[0], "~N(0,1)") ),col=cols[3])
dev.off()
 This chart was created with R.

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20 December 2005

Category:CC-BY-SA-3.0-migrated Category:GFDL Category:Graph images that should use vector graphics Category:License migration completed Category:PNG created with R Category:PNG that should use vector graphics Category:Square-root diffusion