I have a list of spatial buffers (30000 buffers) that I built with the function lapply:

buff.pts <- lapply(1:nrow(pts.prj), FUN=function(l){
  buff <- gBuffer(pts.prj[l,], width=1000) ## 1km

> head(buff.pts)
class       : SpatialPolygons 
features    : 1 
extent      : 307941.8, 311941.8, 4994518, 4998518  (xmin, xmax, ymin, ymax)
coord. ref. : +proj=tmerc +lat_0=0 +lon_0=-73.5 +k=0.9999 +x_0=304800 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs +towgs84=0,0,0 

class       : SpatialPolygons 
features    : 1 
extent      : 307226, 311226, 4991153, 4995153  (xmin, xmax, ymin, ymax)
coord. ref. : +proj=tmerc +lat_0=0 +lon_0=-73.5 +k=0.9999 +x_0=304800 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs +towgs84=0,0,0 

From this list, how can I merge all spatial buffers to obtain a shapefile with the 30000 buffers (or features) ? (This shapefile will then be used in the function aggregate to aggregate spatial polygons by attributes.)

I tested this code but I obtain this error message:

test <- as.data.frame(do.call("rbind", buff.pts))
Error in as.data.frame(do.call("rbind", buff.pts)) : 
  error in evaluating the argument 'x' in selecting a method for function 'as.data.frame': Error in validObject(res) : 
  invalid class “SpatialPolygons” object: non-unique Polygons ID slot values
  • 3
    Any reason you need to build your buffers with lapply instead of using gBuffer with byid = TRUE?
    – cengel
    Commented Feb 14, 2016 at 7:00

3 Answers 3


To merge a list of Spatial objects, you can do:

m <- do.call(bind, buff.pts) 

Given a list of SpatialPolygons objects, here's how to construct a spatial polygons data frame with one feature per original SpatialPolygons feature.

Sample data: spl is a list of 12 SpatialPolygons objects - make sure your object gives the same results as this, and test on a small sample before running on 30,000:

> length(spl)
[1] 12
> class(spl)
[1] "list"
> class(spl[[1]])
[1] "SpatialPolygons"
[1] "sp"

You want to create a single Spatial Polygons object with all the features in it in order to then make a Spatial Polygons Data Frame:

> joined = SpatialPolygons(lapply(spl, function(x){x@polygons[[1]]}))
> plot(joined)

This takes the first polygons slot from the object (and there should be only one, since each list element is currently a single feature) and then constructs a list of Polygons objects which is what you feed to SpatialPolygons to make a multi-feature SpatialPolygons. Plot this, and you should see all your features. Next, if you want to save as a shapefile, you need to add some data. In the absence of anything else, I create a simple 1 to 12 ID column:

> jdata = SpatialPolygonsDataFrame(Sr=joined, data=data.frame(i=1:12),FALSE)

The FALSE flag just stops R trying to rearrange the spatial and non-spatial data to match up. You might want to put the buffer sizes in the data frame or something.

Job done.


You can use the makeUniqueIDs argument in rbind if your polygons do not have unique IDs.


list(buff.pts, makeUniqueIDs = T) %>% 
  flatten() %>% 
  do.call(rbind, .)

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