[R] DEM calculation

[Lars Claussen]

Hello R-World,

i am trying to calculate data for a DEM (Digital Elavation Model) which i
also want to plot in R. i have the coordinates for the lower left corner
which look something like this:

x<-42,2
y<-50,5

besides i have the cellsize of the grid, which is:

z<-1,1

what i do is to calculate the corrdinates of the cells to the right and top,
what i can do by specifying the number of rows and columns. these are
j<-1:805 (columns)
i<-1:616 (rows)

well, to calculate them seperatly is easy:

r<-x+(i-1)*z
h<-y+(j-1)*z

but i can't get it straight how to create a data frame with two rows, one
for the x- the other for the y-coordinate. The problem is, that lots of
values have to be repeated as every first row x-coordinate has the same
y-coordinate and so on.

finally it should look like this:

x y
42,2 50,5
43,3 50,5
44,4 50,5
45,5 50,5
. .
. .
42,2 51,5
43,3 51,5
44,3 51,5

any suggestion? thanks in advance, Lars Claussen

[Eric Lecoutre]

You can use ??expand.grid'

?? expand.grid(x=seq(42.2,45.2,by=1),y=seq(50.5,51.5,by=1))
x y
1 42.2 50.5
2 43.2 50.5
3 44.2 50.5
4 45.2 50.5
5 42.2 51.5
6 43.2 51.5
7 44.2 51.5
8 45.2 51.5


Eric

Eric Lecoutre
UCL / Institut de Statistique
Voie du Roman Pays, 20
1348 Louvain-la-Neuve
Belgium

tel: [phone]
lecoutre at stat.ucl.ac.be
http://www.stat.ucl.ac.be/ISpersonnel/lecoutre

If the statistics are boring, then you've got the wrong numbers. -Edward
Tufte

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Lars Claussen
Sent: jeudi 2 juin 2005 10:56
To: R-help at stat.math.ethz.ch
Subject: [R] DEM calculation
Hello R-World,
i am trying to calculate data for a DEM (Digital Elavation
Model) which i also want to plot in R. i have the coordinates
x<-42,2
y<-50,5
z<-1,1
what i do is to calculate the corrdinates of the cells to the
right and top, what i can do by specifying the number of rows
and columns. these are j<-1:805 (columns) i<-1:616 (rows)
r<-x+(i-1)*z
h<-y+(j-1)*z
but i can't get it straight how to create a data frame with
two rows, one for the x- the other for the y-coordinate. The
problem is, that lots of values have to be repeated as every
first row x-coordinate has the same y-coordinate and so on.
x y
42,2 50,5
43,3 50,5
44,4 50,5
45,5 50,5
. .
. .
42,2 51,5
43,3 51,5
44,3 51,5
any suggestion? thanks in advance, Lars Claussen
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