R help - Dec 2009 - plotting with varying dot sizes

Dear all,

I am trying to plot on a spatial map the punctual measurements of the data
located in the file (https://opengeo.metu.edu.tr/test.csv). I'd like to have
the dots in some way proportional to the magnitudes of the measurements.

I have difficulties with the code given below:  The dot sizes do not vary not
proportionally when varying the coefficient ("0.725"). It either plots
the dots
extremely big or extremely small. Successively running the plot command from
the command line gives each time different results in an unpredictably random
way.

Is this a bug or am I missing something?
Servet

Running R version 2.8.1 (2008-12-22) on Ubuntu 9.10.


******************************************************************************
library(sp)

Insitu = read.table("test.csv", skip=3,sep=",")
Header = read.table("test.csv", skip=1,sep=",",nrows=1)
names(Insitu)= as.character(as.matrix(Header))
CRS_4326 = CRS("+init=epsg:4326")

Insitu_sp <-
SpatialPointsDataFrame(cbind(Insitu[,"Boylam"],Insitu[,"Enlem"]),
data=Insitu, proj4string=CRS_4326)

plot(Insitu_sp[,"SPM"],col="black",pch=19,cex=0.725*sqrt(Insitu["SPM"]))

The symbols function may work better than plot for this situation.

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of servet ahmet ?izmeli
> Sent: Thursday, December 10, 2009 6:18 AM
> To: r-help at r-project.org
> Subject: [R] plotting with varying dot sizes
> 
> Dear all,
> 
> I am trying to plot on a spatial map the punctual measurements of the
> data
> located in the file (https://opengeo.metu.edu.tr/test.csv). I'd like to
> have
> the dots in some way proportional to the magnitudes of the
> measurements.
> 
> I have difficulties with the code given below:  The dot sizes do not
> vary not
> proportionally when varying the coefficient ("0.725"). It either
plots
> the dots
> extremely big or extremely small. Successively running the plot command
> from
> the command line gives each time different results in an unpredictably
> random
> way.
> 
> Is this a bug or am I missing something?
> Servet
> 
> Running R version 2.8.1 (2008-12-22) on Ubuntu 9.10.
> 
> 
> ***********************************************************************
> *******
> library(sp)
> 
> Insitu = read.table("test.csv", skip=3,sep=",")
> Header = read.table("test.csv", skip=1,sep=",",nrows=1)
> names(Insitu)= as.character(as.matrix(Header))
> CRS_4326 = CRS("+init=epsg:4326")
> 
> Insitu_sp <-
>
SpatialPointsDataFrame(cbind(Insitu[,"Boylam"],Insitu[,"Enlem"]),
> data=Insitu, proj4string=CRS_4326)
> 
>
plot(Insitu_sp[,"SPM"],col="black",pch=19,cex=0.725*sqrt(Insitu["SPM"])
> )
> 
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

I think I located the problem. the data frame associated with my spatial object
(Insitu_sp) contains some NAs. And in this case, the function plot does not
like NAs. It simply behaved strangely. The code below did the trick :

idx = is.na(Insitu[,"SPM"])
ptsize = 0.35*(sqrt(Insitu[!idx,"SPM"])+1)
plot(Insitu_sp[!idx,"SPM"],col="red",pch=19,cex=ptsize)

Does the symbols function supports spatial (sp) objects? I could not manage to
make it work with my sp data.



Quoting Greg Snow <Greg.Snow at imail.org>:
> The symbols function may work better than plot for this situation.