Dear Prof. Roger,
Yes, it's really a reasonable reason.
The conversion method mentioned before by me may be not good, because it
used different scale factors for x and y coordinates. A new correct method
may be explored.
Waiting for your good news.
On 9/28/07, Roger Bivand <[EMAIL PROTECTED]> wrote:
>
> Dear Zhijie Zhang,
>
> I'm working on an approach to this. I was asked (also on Tuesday) whether
> it is possible to disguise map position to increase confidentiality for
> patient locations. This is a valid reason to elide spatial position, so
> I'll try to see what can be done, and it will include your case.
>
> I will send a draft version for you to try when I have something that
> seems to work.
>
> Best wishes,
>
> Roger
>
> On Tue, 25 Sep 2007, zhijie zhang wrote:
>
> > Dear Porf. Roger,
> > There are still a little problem with function mess_up().
> > #Programs to read the rivers
> > library(sp);library(foreign);library(maptools)
> >
> > rivers<- readShapeLines("e:/qiupu.shp")
> >
> > #loops
> >
> > lns <- slot(rivers, "lines")
> >
> > new_lns <- lapply(lns, function(x)
> > {
> > Lns <- slot(x, "Lines")
> > new_Lns <- lapply(Lns, function(y)
> > {
> > new_crds <-* mess_up*(slot(y, "coords"))
> > Line(new_crds)
> > })
> > Lines(new_Lns, ID=slot(x, "ID"))
> > })
> > new_rivers <- SpatialLines(new_lns)
> >
> > 1. #for your mess_up() - note, untried.
> > *#Erros: no function mess_up()*
> >
> > 2. #Also note that the projection will not be defined.
> > Actually, i have projected in ARCGIS, so the projection will be
> unneccessary
> > in R.
> >
> > Thanks.
> >
> >
> >
> >
> >
> > On 9/24/07, Roger Bivand <[EMAIL PROTECTED]> wrote:
> >>
> >> On Mon, 24 Sep 2007, zhijie zhang wrote:
> >>
> >>> Dear Roger,
> >>> The reason for doing this is to get more general programs, which can
> be
> >>> used in the other similar conditions. If we can convert all the
> related
> >>> objects into internal [0,1], we can more easily use the intermediate
> >> results
> >>> calculated from unit square,such as .bandwidth in kernels.
> >>
> >> Exactly - with the original data, the units *are* general, because they
> >> are in meters. Provided the other data is also using the same metric,
> this
> >> also permits a direct interpretation of bandwidth, possibly with a
> >> physical or biological basis. In the same sense, you can also get a
> >> relative bandwidth from (bw / max(diff(bbox(<obj>)))), and multiply it
> out
> >> again for a different context.
> >>
> >>> I think the main problem maybe the lines object, that is qiupu.shp.
> The
> >>> scaling factor on the longer axis is from the guichi polygon.
> >>> #read the lines of two rivers in the guichi
> >>> rivers <- readShapeLines("e:/qiupu.shp") #change the
> >> coordinates??difficult
> >>> #plot(rivers,add=T)
> >>> I'm not very sure if they,especially qiupu lines, can be successfullyy
> >>> done.
> >>
> >> Just loops of lapply(), not worse:
> >>
> >> lns <- slot(rivers, "lines")
> >>
> >> new_lns <- lapply(lns, function(x) {
> >> Lns <- slot(x, "Lines")
> >> new_Lns <- lapply(Lns, function(y) {
> >> new_crds <- mess_up(slot(y, "coords"))
> >> Line(new_crds)
> >> })
> >> Lines(new_Lns, ID=slot(x, "ID")
> >> })
> >> new_rivers <- SpatialLines(new_lns)
> >>
> >> for your mess_up() - note, untried. Also note that the projection will
> not
> >> be defined.
> >>
> >> Roger
> >>
> >>> Thanks very much.
> >>>
> >>> On 9/24/07, Roger Bivand <[EMAIL PROTECTED]> wrote:
> >>>>
> >>>> Dear Zhijie Zhang,
> >>>>
> >>>> On Sun, 23 Sep 2007, zhijie zhang wrote:
> >>>>
> >>>>> Dear Roger,
> >>>>> I have a problem on converting the coordinates into interval [0,1],
> >>>> hoping
> >>>>> that you can give me a hand.
> >>>>
> >>>> I think that you need to explain why. If it is just because the
> >>>> coordinates "explode" because they are large, then simply scaling
> like
> >>>> this:
> >>>>
> >>>> library(rgdal)
> >>>> guichi <- readOGR(".", "guichi")
> >>>> plot(guichi, axes=TRUE)
> >>>> bbox(guichi)
> >>>> proj4string(guichi)
> >>>> t1 <- paste("+proj=tmerc +lat_0=0 +lon_0=117 +k=1.000000 +x_0=0",
> >>>> "+y_0=-3348000 +a=6378140 +b=6356755.288157528 +units=km")
> >>>> t2 <- spTransform(guichi, CRS(t1))
> >>>> plot(t2, axes=TRUE)
> >>>> bbox(t2)
> >>>> # min max
> >>>> # r1 10.148541 79.88203
> >>>> # r2 0.834946 61.90978
> >>>>
> >>>> gets down to 70 by 80, which is not such a numerical risk (if need
> be,
> >> use
> >>>> +units=kmi to get nautical miles, which reduces the numbers even
> more).
> >> It
> >>>> has the key advantage that you can always get back to the true
> >> coordinates
> >>>> by transforming back.
> >>>>
> >>>> In the internal code, you will see that many packages guard by using
> >> [-1,
> >>>> +1] on both dimensions. In your case and if you know that you need
> >> this,
> >>>> you would have to work out the scaling factor on the longer axis, so
> >> that
> >>>> points on the shorter axis would be scaled correctly. But if you want
> >> to
> >>>> keep the dimensions' aspect, you could just shift the origin and the
> >> units
> >>>> as I show above.
> >>>>
> >>>> Hope this helps,
> >>>>
> >>>> Roger
> >>>>
> >>>>> My data consist of points(cases), lines(rivers) and polygon (guichi
> >>>> city),
> >>>>> and i want to change their coordinates into interval [0,1]. I have
> >> put
> >>>> the
> >>>>> data in the attachment, so that you can use it.
> >>>>> The following is the programs to read the data and one possible
> method
> >>>> for
> >>>>> conversion:
> >>>>>
> >>>>> library(sp)
> >>>>> library(foreign)
> >>>>> library(mgcv)
> >>>>> library(maptools)
> >>>>>
> >>>>> #read the polygon containing the studied points
> >>>>> guichi <- readShapePoly("e:/guichi.shp") #boundary polygons
> >> containing
> >>>> the
> >>>>> points
> >>>>> point_poly <-
> >>>>>
> >>>>
> >>
> getPolygonCoordsSlot(getPolygonsPolygonsSlot(getSpPpolygonsSlot(guichi)[[1]])[[1]])
> >>>>> #get the coordinates of guichi
> >>>>> #plot(point_poly,xlab="x", ylab="y",type="l")
> >>>>>
> >>>>> #read the lines of two rivers in the guichi
> >>>>> rivers <- readShapeLines("e:/qiupu.shp") #change the
> >>>> coordinates??difficult
> >>>>> #plot(rivers,add=T)
> >>>>>
> >>>>> #read the points of cases and controls
> >>>>> case_control <- read.csv("e:/casecontrol.csv",sep=",", header=TRUE)
> >>>>> #plot(case_control$x,case_control$y)
> >>>>>
> >>>>> *#Plot the whole figure*
> >>>>> plot(point_poly,xlab="x", ylab="y",type="l")
> >>>>> plot(rivers,add=T)
> >>>>> points(case_control$x,case_control$y,add=T)
> >>>>>
> >>>>>
> >>>>
> >>
> ###################################################################################
> >>>>> #one of the possible methods to convert the x/y coordinates into
> >>>> interval
> >>>>> [0,1]
> >>>>> *# But it seems there is a problem: it convert the x/y coordinates
> >> into
> >>>>> interval [0,1], respectively.
> >>>>> # In my opinion, they should be expand or shrink according to the
> >> same
> >>>>> minimum/maximum value*.
> >>>>> st <- function(x)(x-min(x))/(max(x)-min(x))
> >>>>> case_control[,c(8,9)] <- data.frame
> (lapply(case_control[,c(6,7)],st))
> >>>>>
> >>>>
> >>
> ###################################################################################
> >>>>> *Q1. The main problem is on the rivers, which has multiple lines.
> >> There
> >>>> are
> >>>>> difficulties for conversion.
> >>>>> Q2. when i convert the x/y coordinates, i'm not very sure whether i
> >>>> should
> >>>>> use the same scale of conversion or not. *
> >>>>> Could you please help us to solve it?
> >>>>> Any suggestions/help are greatly appreciated.
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>> --
> >>>> Roger Bivand
> >>>> Economic Geography Section, Department of Economics, Norwegian School
> >> of
> >>>> Economics and Business Administration, Helleveien 30, N-5045 Bergen,
> >>>> Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
> >>>> e-mail: [EMAIL PROTECTED]
> >>>>
> >>>
> >>>
> >>>
> >>>
> >>
> >> --
> >> Roger Bivand
> >> Economic Geography Section, Department of Economics, Norwegian School
> of
> >> Economics and Business Administration, Helleveien 30, N-5045 Bergen,
> >> Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
> >> e-mail: [EMAIL PROTECTED]
> >>
> >
> >
> >
> >
>
> --
> Roger Bivand
> Economic Geography Section, Department of Economics, Norwegian School of
> Economics and Business Administration, Helleveien 30, N-5045 Bergen,
> Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
> e-mail: [EMAIL PROTECTED]
>
--
With Kind Regards,
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Zhi Jie,Zhang ,PHD
Tel:86-21-54237149
Dept. of Epidemiology,School of Public Health,Fudan University
Address:No. 138 Yi Xue Yuan Road,Shanghai,China
Postcode:200032
Email:[EMAIL PROTECTED]
Website: www.statABC.com
[***********************************************************************]
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