使用 R 从网格创建点

Question

I hope to achieve a .csv file with a list of coordinates corresponding to the centre of each grid square on a plot .

I've been able to map the polygon and overlay a grid , however I'm not sure what will be required to a) plot points in the centre of each grid square, and b) extract the coordinates from the points - although the later should fall out once a) is complete.

Grid Plot is shown below:

Any suggestions would be appreciated.

  First we need to make a regular grid
      NGSA.grid=spsample(NGSA.union, n = 1000, type="regular", nsig = 2,    offset = c(0.5,0.5),pretty = FALSE)
      str(NGSA.grid)
      gridded(NGSA.grid)=TRUE
      plot(NGSA.grid,pch=19,cex=0.1,col="green",axes=TRUE)
      plot(NGSA.OGR, add=TRUE, pch=16, cex=0.5)
      proj4string(NGSA.grid)==proj4string(NGSA.OGR)

Answer 1

First follow ?readOGR to create the scot_BNG object which I'll be using here.

Then create gridded object:

> scotgrid = spsample(scot_BNG, n=1000, type="regular", nsig=2, pretty=FALSE)
> gridded(scotgrid)=TRUE

Then the coordinates function gets you the grid centres. Note you could just use the scotgrid object created above before you made it a gridded object. At that point its a SpatialPoints object. Anyway:

> head(coordinates(scotgrid))
           x1       x2
[1,] 211728.1 535835.7
[2,] 247407.1 535835.7
[3,] 238487.4 544755.4
[4,] 247407.1 544755.4
[5,] 265246.6 544755.4
[6,] 274166.3 544755.4

And if you want to plot the cell centres over the grid you can just use points , which extracts those cell coordinates before plotting:

> plot(scotgrid)
> points(scotgrid,pch=19,col="red",cex=.25)