[R-sig-Geo] Add layers to a lattice plot via a for loop

[David Wang]

Oops, I didn't run the example in a clean, new session. Here is that an update that should work:


library(maps)
library(maptools)
library(sp)
library(latticeExtra)

coast <- map(fill = TRUE, plot = FALSE)
coast <- map2SpatialLines(coast)
coast <- SpatialLinesDataFrame(coast, data.frame(z = seq_len(length(coast))))
tracks <- list(SpatialPoints(cbind(c(90, 90), c(-20, 20))),
               SpatialPoints(cbind(c(-90, -90), c(-20, 20))))

p <- spplot(coast, col.regions = "darkgray", colorkey = FALSE)
p <- p + layer(sp.points(tracks[[1]], pch = 19, col = 1))
p <- p + layer(sp.points(tracks[[2]], pch = 19, col = 2))
print(p) # shows both tracks

p <- spplot(coast, col.regions = "darkgray", colorkey = FALSE)
for (k in seq_along(tracks))
  p <- p + layer(sp.points(tracks[[k]], pch = 19, col = k))
print(p) # shows the second (red) track only

The R environment is:

> sessionInfo()
R version 3.3.1 (2016-06-21)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

Thanks,

D

________________________________
From: R-sig-Geo <r-sig-geo-bounces at r-project.org> on behalf of Edzer Pebesma <edzer.pebesma at uni-muenster.de>
Sent: Wednesday, November 2, 2016 10:33:31 AM
To: r-sig-geo at r-project.org
Subject: Re: [R-sig-Geo] Add layers to a lattice plot via a for loop



On 02/11/16 14:52, David Wang wrote:
> Hello �kos,
>
>
> Thank you for your suggestion. I'm not sure that solves the problem. But here is a reproducible example:
>
>
> library(maps)
> library(maptools)
> library(sp)
> coast <- map(fill = TRUE, plot = FALSE)
> coast <- map2SpatialLines(coast)
> tracks <- list(SpatialPoints(cbind(c(90, 90), c(-20, 20))),
>                SpatialPoints(cbind(c(-90, -90), c(-20, 20))))
>
> p <- spplot(coast, col.regions = "darkgray", colorkey = FALSE)

Trying to reproduce, here I get:
> p <- spplot(coast, col.regions = "darkgray", colorkey = FALSE)
Error in (function (classes, fdef, mtable)  :
  unable to find an inherited method for function ‘spplot’ for signature
‘"SpatialLines"’


> p <- p + layer(sp.points(tracks[[1]], pch = 19, col = 1))
> p <- p + layer(sp.points(tracks[[2]], pch = 19, col = 2))
> print(p) # this shows both tracks
>
> p <- spplot(coast, col.regions = "darkgray", colorkey = FALSE)
> for (k in seq_along(tracks))
>   p <- p + layer(sp.points(tracks[[k]], pch = 19, col = k))
> print(p) # this shows the second (red) track only
>
> Thanks,
>
> David
>
> ________________________________
> From: R-sig-Geo <r-sig-geo-bounces at r-project.org> on behalf of Bede-Fazekas �kos <bfalevlist at gmail.com>
> Sent: Tuesday, November 1, 2016 6:02:59 PM
> To: r-sig-geo at r-project.org
> Subject: Re: [R-sig-Geo] Add layers to a lattice plot via a for loop
>
> Dear David,
>
> since you have not provided us a reproductable script+dataset, I can't
> check whether my suggestion is connected to your problem. Maybe not...
> Anyway, lattice plotter functions - such as spplot() and its relatives
> -  inside for loops, functions, and tryCatch() blocks usually work in a
> different way than their line-by-line versions. Using print(spplot())
> instead of spplot() can solve the problem.
>
> HTH,
> �kos Bede-Fazekas
> Hungarian Academy of Sciences
>
> 2016.11.01. 21:54 keltez�ssel, David Wang �rta:
>> Hello,
>>
>>
>> I need to overlay a set of tracks (SpatialPoints objects) on a map and thought I would add them one by one to a lattice plot of coastline. However, when I did
>>
>>
>> p <- spplot(coast, xlim = xlim, ylim = ylim, col.regions = "darkgray", colorkey = FALSE)
>> for (k in seq_along(tracks))
>>    p <- p + layer(sp.points(tracks[[k]], pch = 20, col = k))
>> p
>>
>> (where coast is the coastline as a SpatialLines object, and tracks is a list of SpatialPoints objects), p only shows the coastline and the last track. What's perplexing to me is that when I explicitly added layers without using a for loop, the result trellis object p does contain all four tracks in their specific colors:
>>
>>
>>
>>
>> p <- spplot(coast, xlim = xlim, ylim = ylim, col.regions = "darkgray", colorkey = FALSE)
>> p <- p + layer(sp.points(tracks[[1]], pch = 20, col = 1))
>> p <- p + layer(sp.points(tracks[[2]], pch = 20, col = 2))
>> p <- p + layer(sp.points(tracks[[3]], pch = 20, col = 3))
>> p <- p + layer(sp.points(tracks[[4]], pch = 20, col = 4))
>> p
>>
>> Does anyone happen to have a clue why the for loop failed to overlay layers?
>>
>> Thanks,
>> David
>>
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>>
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo at r-project.org
>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>
>
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>
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>
>
>
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--
Edzer Pebesma
Institute for Geoinformatics  (ifgi),  University of Münster
Heisenbergstraße 2, 48149 Münster, Germany; +49 251 83 33081
Journal of Statistical Software:   http://www.jstatsoft.org/
Computers & Geosciences:   http://elsevier.com/locate/cageo/


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