Behavior of v.sort.points

[spawley]

Hello devs,

I appear to be having some problems with the add on v.sort.points. Two issues, potentially bugs:

(1) the module fails if the 'cat' column is not the first attribute in the table (i.e. if points have been generated from a database table), returning the error:

'Error in sqlite3_prepare(): duplicate column name: cat'

(2) even if 'cat' is the first column, sorting by an integer column does not appear to be sorting point datasets in numeric order. Example from the nc_spm location:

v.sort.points input=firestations@PERMANENT output=firestations_sorted column=ID

The order of the points based on opening the attribute table, and the relationship between the 'ID' column and 'cat' appears to be the same as the original dataset, where 'ID' was not in ascending order.

Either I'm doing something wrong or the add on requires some tweaks. Otherwise his would be a very useful tool.

Steve

[mlennert]

In 71147:

v.sort.points: handle non-first key column (fix #3352: Behavior of v.sort.points)

[mlennert]

Replying to spawley:

Hello devs,

I appear to be having some problems with the add on v.sort.points. Two issues, potentially bugs:

(1) the module fails if the 'cat' column is not the first attribute in the table (i.e. if points have been generated from a database table), returning the error:

'Error in sqlite3_prepare(): duplicate column name: cat'

Try r71147. This should hopefully fix that issue.

(2) even if 'cat' is the first column, sorting by an integer column does not appear to be sorting point datasets in numeric order. Example from the nc_spm location:

v.sort.points input=firestations@PERMANENT output=firestations_sorted column=ID

The order of the points based on opening the attribute table, and the relationship between the 'ID' column and 'cat' appears to be the same as the original dataset, where 'ID' was not in ascending order.

This is not a bug: cat values are conserved, i.e. the same points have the same cat value in the input and the output. However, points are in a different order in the file after v.sort.points. Category values of objects do not define order.

Moritz

[mlennert]

Replying to mlennert:

Replying to spawley:

(2) even if 'cat' is the first column, sorting by an integer column does not appear to be sorting point datasets in numeric order. Example from the nc_spm location:

v.sort.points input=firestations@PERMANENT output=firestations_sorted column=ID

The order of the points based on opening the attribute table, and the relationship between the 'ID' column and 'cat' appears to be the same as the original dataset, where 'ID' was not in ascending order.

This is not a bug: cat values are conserved, i.e. the same points have the same cat value in the input and the output. However, points are in a different order in the file after v.sort.points. Category values of objects do not define order.

Try

d.vect map=firestations icon=basic/circle size=0.5 size_column=ID
d.vect map=firestations_sorted icon=basic/circle size=0.5 size_column=ID

and compare the two maps to see the difference.

Moritz