Hi, No the output isn't the same as the original spatstat output, I changed it from scientific to numerical notation in excel. I realised last night that it was probably a rounding issue and have just performed the same analysis (in a much more long-winded way) in arcmap and got the same results, so quadratcount is producing 15m x 15m quadrats! Sorry to cause confusion!
Is the quadratcount only when the results are plotted? I assume the numerical output (show(q15)) is correct? Best Lauren -----Original Message----- From: Adrian Baddeley [mailto:[EMAIL PROTECTED] Sent: 23 October 2008 05:34 To: R-help Forum Cc: Gough Lauren; Rolf Turner Subject: Re: [R] Spatstat help - quadratcount query Gough, Lauren wrote: > >> I am using quadratcount in spatstat to divide a window containing a >> point pattern into a grid of quadrats containing the intensity of >> points in each quadrat. >> However, when I look at the data for quadrat counts it seems the >> function is not keeping the size of the quadrats constant, but is >> instead varying the width of the quadrats (in both the x and y >> direction) between 10m and 20m, meaning that some quadrats are 10m x >> 10m and some are four times the size (20m x 20m) (I have pasted some >> of the output below to demonstrate). This isn't exactly the pasted output from spatstat, is it? The output from spatstat for this window would look something like this: x y [3.4171e+05,3.4172e+05] (3.4172e+05,3.4174e+05] (3.12676e+06,3.12678e+06] 1 0 (3.12675e+06,3.12676e+06] 0 2 (3.12674e+06,3.12675e+06] 0 0 and so on. The row and column labels indicate the boundaries of the quadrats; however, because the coordinates are large numbers, they have been formatted in scientific notation, and ROUNDED to the fourth or fifth decimal place. A number printed as 3.12675e+06 is not always exactly equal to 3126750. It could be anywhere from 3126745 to 3126755. The peculiar impression that the successive differences alternate between 10 and 20, when they should be 15, is an artefact of the rules used for rounding numbers in R. To extract the precise values of the quadrat boundaries, use xbreaks <- attr(q15, "xbreaks") ybreaks <- attr(q15, "ybreaks") Then you can check directly that the breaks are evenly spaced at intervals of 15 units in each direction. Incidentally, please be warned that there is a bug in the plot method plot.quadratcount in spatstat 1.14-4 which causes the counts to be plotted in the wrong quadrats. This will be fixed in the next release spatstat 1.14-5, due shortly. Adrian Baddeley This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
