using a for loop to determine the distance between two points from a uniform distribution

Question

If Xm~uniform(-25,25),Ym~uniform(-25,25) and r~uniform(0,25), θ~uniform(0,2π) and Xf=rcosθ, Yf=rsinθ.

I want to use a for loop to create 5000 independent variables of point (Xm,Ym) and (Xf,Yf) then calculate the distance between the two points. i know how to calculate the distance between points but creating 5000 realisations of (Xm,Ym) and (Xf,Yf) I am finding tricky. here is my attempt:

Now for Xf,Yf I took a similar approach to Xm,Ym

for (i in 1:5000) { res=c() repeat{ Xm=runif(1,min=-25,max=25) Ym=runif(1,min=-25,max=25) if(Xm**2+Ym**2<=25**2) res=rbind(res,data.frame(Xm,Ym)) break { res=rbind(res,data.frame(Xm,Ym)) } for (i in 1:5000) { res=c() repeat{ R=runif(1,min=0,max=25) 0=runif(1,min=0,max=2*pi) Xf=Rcos(0) Yf=Rsin(0) Yf=runif(1,min=-25,max=25) if(Xf**2+Yf**2<=25**2) res=rbind(res,data.frame(Xf,Yf)) break { res=rbind(res,data.frame(Xf,Yf)) } D=sqrt((Xm-Xf)**2+(Ym-Yf)**2))

Do you really need it to be a loop? You can use sample() to get 5000 points of Xm or in the same runif(n=5000) — vpz
– vpz, Commented Mar 19, 2020 at 3:24

vpz · Accepted Answer · 2020-03-19 03:38:03Z

Here is an approach without loop:

# Yours data set.seed(9) # Just for reprodutibility npoints = 5000 # Vectors with 5000 points Xm=runif(n = npoints,min=-25,max=25) Ym=runif(n = npoints,min=-25,max=25) theta = runif(n = npoints, min = 0, max = 2*pi) R = runif(n = npoints,min = 0, max = 25) Xf = R*cos(theta) Yf = R*sin(theta) D = sqrt((Xm-Xf)^2+(Ym-Yf)^2)

Collectives™ on Stack Overflow

using a for loop to determine the distance between two points from a uniform distribution

1 Answer 1

Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Related