Difference between revisions of "Generate a grid with sequential numbers"
From GRASS-Wiki
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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` |
| − | # | + | #(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.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:
