dynamic (interactive) representation of several GPS trajectories

In addition to Roman's suggestion, I tweaked the function 'plot.ltraj' to
successfully implement a non-interactive version of what (I think) you
want, that is a video (for an interactive version of it, keep reading and
see below, but there would be only one individual unfortunately). Among a
few other things, the function now allows to plot all (selected)
individuals on the same plot (argument 'by = "none"), which is relevant for
your purpose. It also allow you to modify point/line graphical settings.

The modified function is available in the package "hab":

http://ase-research.org/basille/hab

(probably better to install the one from GitHub directly)

Keep in mind that this is not a package as stable as adehabitatLT. I do my
best, but use at your own risks! ;)

Now, if you would like to export a video, you could use the modified
'plot.ltraj' to do essentially the following steps:

* prepare a time sequence
* use this sequence to loop over the whole ltraj, subset the relevant time
period, and plot it
* export as PNG at each step
* use ffmpeg to convert it in mp4 video

The resulting video looks like this:

http://ase-research.org/basille/pres/Basille_FLREC_2014/video/wost.mp4

or that:

http://ase-research.org/basille/pres/Basille_FLREC_
2014/video/wost-dark.mp4

with different graphical parameters. In details (but you'll have to adjust
it to your own data), it goes like this ['wlt' is the ltraj object]:

## ================================================ ##
## Load 'hab' and 'lubridate' (for time management)
library(hab)
library(lubridate)

## Prepare the sequence (tseq12 every 12 hours)
tseq12 <- seq(ymd("20090301"), ymd("20111231"), by = 3600*12)
length(tseq12)

## Prepare the graphical parameters with the complete plot
library(RColorBrewer)
wcol <- brewer.pal(8, "Dark2")
names(wcol) <- burst(wlt)
par(mar = c(0, 0, 0, 0), bg = "#3b3f43")
plot(wlt, by = "none", axes = FALSE, ppar = list(pch = 20, col = wcol),
lpar = list(col = wcol, lwd = 3), spoldf = wMapc, spoldfpar = list(col =
"#ecececff", border = NA), final = FALSE)
text(x = 0, y = 3000000, label = paste(month(tseq12[1], label = TRUE),
year(tseq12[1]), sep = "\n"), cex = 3, col = "#ecececff")

## And plot windows of 5 days in a loop
library(Cairo)
for (i in 1:length(tseq12)) {
    CairoPNG(filename = paste0("img/wost", sprintf("%05d", i),
        ".png"), bg = "#fdfbf4ff", width = 1000, height = 1000)
    par(mar = c(0, 0, 0, 0), bg = "#fdfbf4ff")
    plot(subset(wlt, date >= tseq12[i] & date < tseq12[i] + 3600 *
        24 * 5), by = "none", axes = FALSE, ppar = list(pch = 20,
        col = wcol, cex = 4), lpar = list(col = wcol, lwd = 12),
        spoldf = wMapc, spoldfpar = list(col = "white", border =
"#a6a6a6ff", lwd = 3),
        final = FALSE, xlim = range(coordinates(wostsub)[, "x"]),
        ylim = range(coordinates(wostsub)[, "y"]))
    text(x = 0, y = 3e+06, label = paste(month(tseq12[i], label = TRUE),
        year(tseq12[i]), sep = "\n"), cex = 6, col = "#a6a6a6ff")
    dev.off()
}

## Finally convert to a video with ffmpeg
## https://trac.ffmpeg.org/wiki/Create%20a%20video%
20slideshow%20from%20images
system("ffmpeg -r 0.3 -framerate 30 -i img/wost%05d.png -c:v libx264
-pix_fmt yuv420p video/wost.mp4")
## ================================================ ##

Looks quite complicated, but I promise it's not that difficult!

Now for the interactive version: I also tweaked 'trajdyn' quite a bit: it
allows to display only a given number of steps, increment by a given number
of steps, change point/line graphical parameters, etc. *But* it doesn't
allow to display several bursts/individuals at once, just as 'plot.ltraj'
now does... This is a strong limitation to what you want to achieve, and
I'm afraid that implementing it (which would be interesting, but I did not
have that in mind yet) would be a tremendous work.

Hope this helps,
Mathieu.


Le 20/02/2015 05:43, Gabriele Cozzi a ?crit :

 Dear list,

I have relocation data for about 20 individuals (ID) for a total of about
70K rows organised in the following data frame:
timevar <-as.numeric(Timestamp); SB is categorical with 2 levels, the
other
variables are self-explanatory I think

ID       Date        Time           Timestamp              Lon       Lat
          Alti SB timevar
D 2013-01-01 18:40:00 2013-01-01 18:40:00 21.85803 -26.99953 917  0
1500
D 2013-01-01 18:55:00 2013-01-01 18:55:00 21.85877 -27.00000 921  0
2400
D 2013-01-01 19:10:00 2013-01-01 19:10:00 21.85907 -27.00015 925  0
3300
A 2013-01-01 19:27:00 2013-01-01 19:27:00 21.85875 -27.00142 922  1
4320
A 2013-01-02 06:40:00 2013-01-02 06:40:00 21.85872 -27.00142 919  1
 44700
A 2013-01-02 06:55:00 2013-01-02 06:55:00 21.86060 -27.00090 916  0
 45600
..    ...............     ...........           ......................
    ........      .........      ....  ..    ......

What I would like to do is to create an animated plot where I can see how
the various individuals move in relationship to each other.

The gvisMotionChart() function from the googleVis package does what I need
on a small subset of my data but it crashes if I try to do the same on the
entire data set.

A reproducible example for two individuals:
      x <- rnorm(40, 21, 0.5)
      y <- rnorm(40, -27, 0.5)
      ID <- rep(c("A","B"), each=20)
      Alt <- floor(rnorm(40, 900, 10))
      tvar <- 1:40
      tvarA <- sample(tvar,20)
      tvarB <- setdiff(tvar, tvarA)

      DF <- data.frame(ID,x,y,Alt,tvar = c(tvarA,tvarB))
      DF <- DF[order(DF$ID,DF$tvar),]

      library(googleVis)
      plot(gvisMotionChart(DF, idvar="ID", timevar= "tvar"))


An alternative along the lines of what I want would be  the
trajdyn{adehabitatLT}, even if it does not allow dynamic movements of more
than one individual at the time, which is unfortunate in my case.

Any suggestion regarding alternative packages/functions is highly
appreciated.

Thanks in advance,
Gabriele

--

~$ whoami
Mathieu Basille
http://ase-research.org/basille

~$ locate --details
University of Florida \\
Fort Lauderdale Research and Education Center
(+1) 954-577-6314

~$ fortune
? Le tout est de tout dire, et je manque de mots
Et je manque de temps, et je manque d'audace. ?
 -- Paul ?luard

--

~$ whoami
Mathieu Basille
http://ase-research.org/basille

~$ locate --details
University of Florida \\
Fort Lauderdale Research and Education Center
(+1) 954-577-6314

~$ fortune
? Le tout est de tout dire, et je manque de mots
Et je manque de temps, et je manque d'audace. ?
 -- Paul ?luard