[R] help to make a map on R
Ronaldo Reis Jr.
chrysopa at insecta.ufv.br
Wed Oct 2 21:26:50 CEST 2002
Hi all,
I need a little help for construct an state's map on R.
The first problem is to get the data.
I have a datafile of longitude and latitude in the follow format:
trajectory latitude longtude
T -22.045618 -51.287056
T -22.067078 -51.265888
T -22.067039 -51.207249
T -22.059690 -48.089695
T -22.075529 -48.074608
T -22.072460 -48.044472
T -22.062767 -48.298473
T -22.077349 -48.322140
T -22.047001 -48.347443
T -22.054266 -48.369331
T -22.042810 -48.392612
T -22.064812 -48.422195
T -22.062544 -48.443497
To read a file is simple, but I need that R change the value of
trajectory after a blank line, reading something like this:
trajectory latitude longitude
T1 -22.045618 -51.287056
T1 -22.067078 -51.265888
T1 -22.067039 -51.207249
T2 -22.059690 -48.089695
T2 -22.075529 -48.074608
T2 -22.072460 -48.044472
T3 -22.062767 -48.298473
T3 -22.077349 -48.322140
T3 -22.047001 -48.347443
T3 -22.054266 -48.369331
T3 -22.042810 -48.392612
T3 -22.064812 -48.422195
T3 -22.062544 -48.443497
Each trajectory is a line that is a little piece of my map.
After this, to make a map I execute:
tapply() for separate the coordinates for each trajectory, something like
this:
> longitude <- tapply(longitude,trajectory,c)
> longitude
$T1
[1] -51.2871 -51.2659 -51.2072
$T2
[1] -48.0897 -48.0746 -48.0445
$T3
[1] -48.2985 -48.3221 -48.3474 -48.3693 -48.3926 -48.4222 -48.4435
> latitude <- tapply(latitude,trajectory,c)
> latitude
$T1
[1] -22.0456 -22.0671 -22.0670
$T2
[1] -22.0597 -22.0755 -22.0725
$T3
[1] -22.0628 -22.0773 -22.0470 -22.0543 -22.0428 -22.0648 -22.0625
The nest step is to make a plot with the coordinates.
> plot(longitude,latitude, asp = 1, type = "n")
And finally plot the lines for each trajectory, and all lines together,
make a Sao Paulo's map and your cities limits.
> lines(longitude$T1,latitude$T1)
> lines(longitude$T2,latitude$T2)
> lines(longitude$T3,latitude$T3)
How can I make to automatized this process? Because I can about 3000
trajectory.
Any other idea for make this is welcome.
Thanks for all
Inte mais
Ronaldo
--
And Bruce is effectively building BruceIX
-- Alan Cox
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