[R] Warning messages in Splancs package :: no non-missing arguments to min; returning Inf

[D]

Hi,

I would need some help with the splans package in R.

I am using a Shapefile (downloadable at)
http://rapidshare.com/files/215206891/Redlands_Crime.zip

and the following execution code

setwd("C:\\Documents and
Settings\\Dejan\\Desktop\\GIS\\assignment6\\DataSet_Redlands_Crime\\Redlands_Crime")
library(foreign)
library(splancs)
auto_xy<-read.dbf("Auto_theft_98.dbf")
rob_xy<-read.dbf("Robbery_98.dbf")
auto.spp<-as.points(auto_xy$x/1000, auto_xy$y/1000)
rob.spp<-as.points(rob_xy$x/1000, rob_xy$y/1000)
image(kernel2d(auto.spp, bbox(auto.spp), h0=4, nx=100, ny=100),
col=terrain.colors(10))
pointmap(auto.spp, col="red", add=TRUE)

I would need to analyze the relationship betweeb the two Shapefiles,
but I am receiving the following warning message and a blank output

Xrange is 1827.026 6796.202
Yrange is 1853.896 6832.343
Doing quartic kernel
Warning messages:
1: In min(x) : no non-missing arguments to min; returning Inf
2: In max(x) : no non-missing arguments to max; returning -Inf

Can someone help me with what am I doing wrong in the execution code?
I am getting a blank graph.

Best regards,
D

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[Barry Rowlingson]

Well, do some investigation. Does the error come from the kernel2d
function, or from the image function? Does it do that for any data
points? Have you read the help for kernel2d? Have you tried the
example in the help(kernel2d) text? Have you ever had it work? What
version of R are you using and so on. Please read the posting guide.

The manual for kernel2d says that the second argument has to be "A
splancs polygon data set". But you've given it bbox(auto.spp). But
bbox returns a matrix which is the wrong structure - the columns are
min and max and the rows are X and Y. Plus it only has the corner
points, not all four points of the box which splancs says it needs.
There's also a clue in your output:

Xrange is  1827.026 6796.202
Yrange is  1853.896 6832.343

- but if you plot the points (which you should always do, to make
sure you've read them in properly) you should see that the X range
should be 6796 to 6832 and the Y range should be 1827 to 1853.

Solution: use the splancs bboxx() function that converts an sp-style
bounding box to a splancs-style bounding box:

k = kernel2d(auto.spp, bboxx(bbox(auto.spp)), h0=4, nx=100, ny=100)
image(k)

Barry

[D]

Dear Barry,

I am new to R and I am sorry for the sens information. I am using R
2.8.1 for Windows.

Does the error come from the kernel2d function, or from the image function?

-- It comes from the kernel2d function.

Does it do that for any data points?

-- Not yet tried with other data, only two mentioned Shapefiles. They
are correctly structured.

Have you read the help for kernel2d? Have you tried the example in the
help(kernel2d) text?

-- I will look into it, thanks!

Have you ever had it work?

-- No, tries on two separate installations.

Thanks for the solution, I will test it right away.

Dejan