##### https://github.com/maartenpaul/DBD_tracking

Revision

**19f3a47289830cf5dc139061a89627b6165da804**authored by Maarten Paul on**19 July 2021, 11:05:43 UTC**, committed by GitHub on**19 July 2021, 11:05:43 UTC****1 parent**fc61c80

Tip revision:

**19f3a47289830cf5dc139061a89627b6165da804**authored by**Maarten Paul**on**19 July 2021, 11:05:43 UTC****Update merge_datasets.R** Tip revision:

**19f3a47** MSD.R

```
track_msd <- function(x,n=5,framerate=0.1,pxsize=100,truncate=F,dim=2){
if (dim==2){ #for 2D data
x$X <- (x$X*pxsize)/1000 #convert pixelsize to um
x$Y <- (x$Y*pxsize)/1000
} else if (dim==3){ #for 3D data
x$X <- (x$X*pxsize[1])/1000 #convert pixelsize to um
x$Y <- (x$Y*pxsize[2])/1000
x$Z <- (x$Z*pxsize[3])/1000
}
#calculate MSD for n time intervals
coef <- ddply(x,.variables = "track",.fun= function(x) {
result <- vector(length = n)
#put first frame of track at zero
x$frame <- x$frame-x$frame[1]+1
if(nrow(x)>n+1){ #test effect of truncating tracks to first number of steps, skipped by default
if(truncate){
x <- x[1:6,]
}
#loop over different time intervals
sapply(1:n,function(j){
#loop over all steps of tracks
sum <- unlist(sapply(1:nrow(x),simplify = F,function(k){
if (is.element(x[k,1]+j,x[,1])){ #check if point is present in track, this deals with gaps
which_point <- which(x[,1]==x[k,1]+j)
if (dim==2){
sum <- ((x[k,2]-x[which_point,2])^2+(x[k,3]-x[which_point,3])^2) #determine squared displacement between points
} else if (dim==3){
sum <- ((x[k,2]-x[which_point,2])^2+(x[k,3]-x[which_point,3])^2+(x[k,5]-x[which_point,5])^2)
}
return(sum)
}}))
result[j] <<- mean(sum) #calculate MSD for j time interval
})
return(result) #return MSD for different time intervals as vector
}
})
return(coef)
}
TRACK_MSD <- function(x,n=5,framerate=0.1,pxsize=100,truncate=F,dim=2){
UseMethod("TRACK_MSD")
}
TRACK_MSD.default <- function(x,n=5,framerate=0.1,pxsize=100,truncate=F,dim=2){
stop("MSD requires data frame")
}
TRACK_MSD.data.frame <- function(x,n=5,framerate=0.1,pxsize=100,truncate=F,dim=2){
track_msd(x,n,framerate,pxsize,truncate,dim)
}
TRACK_MSD.list <- function(x,n=5,framerate=0.1,pxsize=100,truncate=F,dim=2){
llply(x,function(x){
out <- TRACK_MSD(x,n,framerate,pxsize,truncate,dim)
out$cellID <- x$cellID[1]
return(out)
})
}
```

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