Re: [R] Point pattern to grid
On Thu, 17 Nov 2005, Leaf Sun wrote: Dear all, I'd like to change a point pattern to a grid of cells and use one of the variables as the output. e.g. The point pattern is of a window of (500*500) and several features such as pH, SoilType etc. I like to divide it into a grid with cell size 5*5, and use the mean of the point values falling inside the cell as the output. Is there any package in R working with this? Thanks in advance! This might have been better posted on R-sig-geo. Try this: library(sp) df1 - data.frame(x=runif(1,0,500), y=runif(1,0,500), z=rnorm(1)) coordinates(df1) - c(x, y) summary(df1) # SpatialPointsDataFrame grd - GridTopology(c(2.5,2.5), c(5,5), c(100,100)) sgrd - SpatialGrid(grd) #SpatialGrid bbox(sgrd) res - overlay(sgrd, df1) # find which grid cells the points are in str(res) try0 - lapply(split(as(df1, data.frame), res), mean) # take means by grid cell - assumes all numeric columns in df1 # (soil type??) - maybe write a custom function to handle non-numeric # columns sensibly try01 - vector(mode=list, length=prod(slot(slot(sgrd, grid), cells.dim))) nafill - rep(as.numeric(NA), ncol(as(df1, data.frame))) try01 - lapply(try01, function(x) nafill) # make a container to put the means in with the right number of columns try01[as.integer(names(try0))] - try0 # insert means into correct list elements try1 - data.frame(t(data.frame(try01))) # transpose summary(try1) sgrd1 - SpatialGridDataFrame(slot(sgrd, grid), try1) image(sgrd1, x) image(sgrd1, y) image(sgrd1, z) It goes a bit further than the short description of the sp package in the latest R-News, and will most likely be a new method for overlay in sp. If these are your 200K points, it may take a little longer ... Cheers, Leaf -- 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] __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] Point pattern to grid
Hi Roger, Thanks again for your kind help. Yes, I still use the 200K points data applying this program but the good thing is I found it finished in no time. The questions again here are: 1) try0 - lapply(split(as(df1, data.frame), res), mean) When I tried to replace mean to sum, error looks like this: Error in [EMAIL PROTECTED], i, drop = FALSE] : undefined columns selected 2) If I just need to know the number of points in each cells, how can I modify the codes. The codes still a bit beyond me. Thanks! Leaf === At 2005-11-18, 01:39:05 you wrote: === On Thu, 17 Nov 2005, Leaf Sun wrote: Dear all, I'd like to change a point pattern to a grid of cells and use one of the variables as the output. e.g. The point pattern is of a window of (500*500) and several features such as pH, SoilType etc. I like to divide it into a grid with cell size 5*5, and use the mean of the point values falling inside the cell as the output. Is there any package in R working with this? Thanks in advance! This might have been better posted on R-sig-geo. Try this: library(sp) df1 - data.frame(x=runif(1,0,500), y=runif(1,0,500), z=rnorm(1)) coordinates(df1) - c(x, y) summary(df1) # SpatialPointsDataFrame grd - GridTopology(c(2.5,2.5), c(5,5), c(100,100)) sgrd - SpatialGrid(grd) #SpatialGrid bbox(sgrd) res - overlay(sgrd, df1) # find which grid cells the points are in str(res) try0 - lapply(split(as(df1, data.frame), res), mean) # take means by grid cell - assumes all numeric columns in df1 # (soil type??) - maybe write a custom function to handle non-numeric # columns sensibly try01 - vector(mode=list, length=prod(slot(slot(sgrd, grid), cells.dim))) nafill - rep(as.numeric(NA), ncol(as(df1, data.frame))) try01 - lapply(try01, function(x) nafill) # make a container to put the means in with the right number of columns try01[as.integer(names(try0))] - try0 # insert means into correct list elements try1 - data.frame(t(data.frame(try01))) # transpose summary(try1) sgrd1 - SpatialGridDataFrame(slot(sgrd, grid), try1) image(sgrd1, x) image(sgrd1, y) image(sgrd1, z) It goes a bit further than the short description of the sp package in the latest R-News, and will most likely be a new method for overlay in sp. If these are your 200K points, it may take a little longer ... Cheers, Leaf -- 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] = = = = = = = = = = = = = = = = = = = = __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] Point pattern to grid
On Fri, 18 Nov 2005, Leaf Sun wrote: Hi Roger, Thanks again for your kind help. Yes, I still use the 200K points data applying this program but the good thing is I found it finished in no time. The reply is on R-sig-geo. The questions again here are: 1) try0 - lapply(split(as(df1, data.frame), res), mean) When I tried to replace mean to sum, error looks like this: Error in [EMAIL PROTECTED], i, drop = FALSE] : undefined columns selected 2) If I just need to know the number of points in each cells, how can I modify the codes. The codes still a bit beyond me. Thanks! Leaf === At 2005-11-18, 01:39:05 you wrote: === On Thu, 17 Nov 2005, Leaf Sun wrote: Dear all, I'd like to change a point pattern to a grid of cells and use one of the variables as the output. e.g. The point pattern is of a window of (500*500) and several features such as pH, SoilType etc. I like to divide it into a grid with cell size 5*5, and use the mean of the point values falling inside the cell as the output. Is there any package in R working with this? Thanks in advance! This might have been better posted on R-sig-geo. Try this: library(sp) df1 - data.frame(x=runif(1,0,500), y=runif(1,0,500), z=rnorm(1)) coordinates(df1) - c(x, y) summary(df1) # SpatialPointsDataFrame grd - GridTopology(c(2.5,2.5), c(5,5), c(100,100)) sgrd - SpatialGrid(grd) #SpatialGrid bbox(sgrd) res - overlay(sgrd, df1) # find which grid cells the points are in str(res) try0 - lapply(split(as(df1, data.frame), res), mean) # take means by grid cell - assumes all numeric columns in df1 # (soil type??) - maybe write a custom function to handle non-numeric # columns sensibly try01 - vector(mode=list, length=prod(slot(slot(sgrd, grid), cells.dim))) nafill - rep(as.numeric(NA), ncol(as(df1, data.frame))) try01 - lapply(try01, function(x) nafill) # make a container to put the means in with the right number of columns try01[as.integer(names(try0))] - try0 # insert means into correct list elements try1 - data.frame(t(data.frame(try01))) # transpose summary(try1) sgrd1 - SpatialGridDataFrame(slot(sgrd, grid), try1) image(sgrd1, x) image(sgrd1, y) image(sgrd1, z) It goes a bit further than the short description of the sp package in the latest R-News, and will most likely be a new method for overlay in sp. If these are your 200K points, it may take a little longer ... Cheers, Leaf -- 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] __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
[R] Point pattern to grid
Dear all, I'd like to change a point pattern to a grid of cells and use one of the variables as the output. e.g. The point pattern is of a window of (500*500) and several features such as pH, SoilType etc. I like to divide it into a grid with cell size 5*5, and use the mean of the point values falling inside the cell as the output. Is there any package in R working with this? Thanks in advance! Cheers, Leaf __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
