Difference between revisions of "Generate a grid with sequential numbers"

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<source lang="bash">
 
<source lang="bash">
# get rows and cols as environment variables
+
# In a shell get rows and cols as environment variables
eval `g.region -g`
+
eval `g.region -g`
  
# generate the grid
+
#(or just note the output of g.region -p and replace either $rows or $cols in the formulas below)
r.mapcalc "grid_seq = col() * $rows + row() + $cols - ($rows + $cols)"
 
  
 +
# generate the a vertical grid (see image below)
 +
r.mapcalc "grid_seq = col() * $rows + row() - $rows"
 +
 +
#or generate a horizontal grid
 +
r.mapcalc "grid_seq = row() * $cols + col() - $cols"
 +
 +
#to visualise the category numbers in the grid
 
d.mon x0
 
d.mon x0
 
d.rast.num grid_seq
 
d.rast.num grid_seq
 
</source>
 
</source>
  
The resulting raster map looks like this:
+
The resulting raster map of a vertical grid looks like this:
  
 
[[File:Raster_grid_seq.png|300px|thumb|left|Sequentially numbered raster grid]]
 
[[File:Raster_grid_seq.png|300px|thumb|left|Sequentially numbered raster grid]]
  
 
[[Category: FAQ]]
 
[[Category: FAQ]]

Latest revision as of 03:45, 19 September 2012

Q: How to generate a grid where the cell numbers are sequential?

A: You can use g.region and r.mapcalc for this:

# In a shell get rows and cols as environment variables
 eval `g.region -g`

#(or just note the output of g.region -p and replace either $rows or $cols in the formulas below)

# generate the a vertical grid (see image below)
r.mapcalc "grid_seq = col() * $rows + row() - $rows"

#or generate a horizontal grid
r.mapcalc "grid_seq = row() * $cols + col() - $cols"

#to visualise the category numbers in the grid
d.mon x0
d.rast.num grid_seq

The resulting raster map of a vertical grid looks like this:

Sequentially numbered raster grid