[R] matrix from sequences
Spencer Graves
spencer.graves at pdf.com
Fri Feb 14 22:19:06 CET 2003
Hi, Miha:
1. How do I get the GRASS library? "library(GRASS)" produced "Error in
library(GRASS) : There is no package called `GRASS'" for me from R 1.6.2
for Windows.
2. I assume there is a typographical error in the last line of your
email: If G$xseq and $yseq are coordinates of points, then
length(G$xseq) == length(G$yseq)??? In that case,
'as.matrix(G[,c("xseq", "yseq")])' should give you what you want.
Or am I missing something?
Best Wishes,
Spencer Graves
Miha STAUT wrote:
>> Miha STAUT wrote:
>>
>>> Hi all,
>>>
>>> I have a data frame with sequences of x and y from a map. I would
>>> like to know it both ways:
>>> 1. How to make a matrix from that;
>>> 2. how to make a data frame of all points in a map.
>>>
>>> Probably it is a silly question, but please tell me where to read
>>> about it or tell me how to do it.
>>>
>>> Miha Staut
>>>
>>> ______________________________________________
>>> R-help at stat.math.ethz.ch mailing list
>>> http://www.stat.math.ethz.ch/mailman/listinfo/r-help
>>>
>> Hi Miha,
>>
>> 1) What is the structure of your data.frame ? Assuming all
>> co-ordinates are in the same column (one column for x and one column
>> for y), the simplest way to extract them and turn them into a matrix
>> would be:
>>
>> as.matrix(mydata[ , c("x", "y")])
>>
>> e.g.:
>>
>> R>mydata <- data.frame(x = rnorm(10), y = rnorm(10), z = rnorm(10))
>> R>mydata
>> x y z
>> 1 -0.73735224 -0.51218243 -0.9602624
>> 2 -1.46079091 -0.63634091 1.4967066
>> 3 -0.28574919 -1.30719383 -0.2887403
>> 4 0.04137159 0.61711350 -0.7057102
>> 5 0.03179303 0.05734869 -0.4637660
>> 6 -0.06638058 -0.74565157 0.9239402
>> 7 -0.67611541 -1.01760810 -0.2854017
>> 8 0.34215052 0.30564550 0.6931193
>> 9 0.83597837 0.75443762 -2.3394679
>> 10 -0.14967073 -0.02027512 -0.1143414
>> R>as.matrix(mydata[ , c("x", "y")])
>> x y
>> 1 -0.73735224 -0.51218243
>> 2 -1.46079091 -0.63634091
>> 3 -0.28574919 -1.30719383
>> 4 0.04137159 0.61711350
>> 5 0.03179303 0.05734869
>> 6 -0.06638058 -0.74565157
>> 7 -0.67611541 -1.01760810
>> 8 0.34215052 0.30564550
>> 9 0.83597837 0.75443762
>> 10 -0.14967073 -0.02027512
>>
>>
>> 2) How are the points stored ? If in a matrix, say mat, with 2 columns
>> for x and y, simply:
>>
>> as.data.frame(mat)
>>
>> Best,
>>
>> Renaud
>
>
>
> Thanks to both of you (Dr Renaud Lancelot and James Holtman)
>
> I see I formulated the question in a wrong way. I got from GRASS the
> coordinates of a map. There is a package in R named GRASS to connect R
> with GRASS.
>
> library(GRASS)
> G<-gmeta() # copy the environment from GRASS
>
> Now G is a data frame containig also $xseq and $yseq which would be the
> coordinates of all the points in x and y direction. The final matrix
> should have length(G$xseq) * length(G$yseq) points.
>
> Miha Staut
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> http://www.stat.math.ethz.ch/mailman/listinfo/r-help
More information about the R-help
mailing list