[R] help to use ppp in spatial analysis

[Ricardo Perrone]

Hi,

i am using spatstat package for spatial data analysis and now i have a problem to create a point pattern. The points are in file "points.txt" (first column for Latitude and second column for Longitude ) and I imported them and separated each columns in two arrays x and y.  If I plots x and y ( e.g  plot(x,y) ) the result appears in square area without problems and the scale is adequate to visual analysis of points ploted. But if i try to use ppp function to create a point pattern the result appears in rectangle area with a poor scale, dificulting in this case the analysis of the points. I think that is probably because of xrange and yrange parameter of ppp function, that was calculated based on max and min values of both x and y, but i am not sure:

latitude <- dataset$V2
longitude <- dataset$V3
xrange <-c(min(longitude), max(longitude))
yrange <-c(min(latitude), max(latitude))

area <- ppp(longitude/10000, latitude/100000, xrange, yrange)  /* there are 181 point in file */
plot(longitude, latitude)       / * square area of visualisation has an adequate scale to analysis */
plot(area)       /* poor rectangle area of visualisation showing point too concentrated and hiding details - possible hot spots */


Is there a way of automatically define the size of window parameter (owin object) in ppp function from dataset of points? How can i scale the window without problems like:
 "warning message: 181 points were rejected as lying outside the specified window"

Thanks
Ricardo