Add a feature to calculate field values in attribut tables

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Author Name: Redmine Admin (Redmine Admin)
Original Redmine Issue: 243

Redmine category:data_provider
Assignee: Gary Sherman

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Add a feature to calculate field values in attribut tables

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• Screenshot-2.png (Giovanni Manghi)

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Author Name: Gavin Macaulay - (Gavin Macaulay -)

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Can you provide some more details on what you mean?

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Author Name: Redmine Admin (Redmine Admin)

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Often I need to calculate new field values based on existing layer attribute table fields. For this issue it would be great if I do have a field calculator. Think about the following situation:

1. open layer attribute table.
2. start digitizing.
3. add a new field NEWFIELD to the opened attribute table if you don't like to overwrite existing table field values.
4. select the field you want to calculate values for. In our case NEWFIELD.
5. open the field calculator. (Opening the field calculator via button like the add field button).
6. select a math function to calculate the NEWFIELD value. p.e. NEWFIELD = sin(EXISTINGFIELD1) + cos(EXISTINGFIELD2)
7. stop digitizing.

Please let me know whether my details do explain my idea.

[qgib]

Author Name: Tim Sutton (Tim Sutton)

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Changed to minor under the following scheme:

• blocker - bugs that should block the release. Since we are going to release pretty much 'come what may' I would like no bugs
• allocated to this category without consultation with me and / or PSC
• critical - bugs that cause the application to crash or corrupt data
• major - application features that do not function at all
• minor - features that function but imerfectly e.g. labels placing incorrectly
• trivial - gui useability issues or small issues with the documentation, install notes etc.

[qgib]

Author Name: Paolo Cavallini (@pcav)

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Looks like you want to reimplement a spreadsheet within QGIS? This can be done eg in OOo, the issue could be how to recall a spreadsheet easily (single-click) from QGIS?

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Author Name: Horst Düster (@hdus)

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Replying to [comment:5 pcav]:

Looks like you want to reimplement a spreadsheet within QGIS? This can be done eg in OOo, the issue could be how to recall a spreadsheet easily (single-click) from QGIS?

It's not the idea to reimplement a spreadsheet! But it is very helpful to calculate new column values. P.e. for Classification of objects. The first part of my request, add a new column, is realised (PostGIS Layer)

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Author Name: cdavilam - (cdavilam -)

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Replying to [comment:5 pcav]:

Looks like you want to reimplement a spreadsheet within QGIS? This can be done eg in OOo, the issue could be how to recall a spreadsheet easily (single-click) from QGIS?

Although it can be done in a spreadsheet, it would be very useful enabling it within QGIS. Otherwise it's necessary to remove the layer/close project->open dbf in OOo->edit and save->reload in QGIS/reopen project->rearrange simbology (if you don't have it saved), which is a very annoying process.

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Author Name: Paolo Cavallini (@pcav)

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Isn't this implemented as a python plugin? Should we close this?

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Author Name: Horst Düster (@hdus)

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Replying to [comment:9 pcav]:

Isn't this implemented as a python plugin? Should we close this?
Which plugin do you mean?

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Author Name: Paolo Cavallini (@pcav)

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Table Manager, by Borys. Please check whether it has the functions you need.

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Author Name: cdavilam - (cdavilam -)

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No, it has a Calculate button, but currently not functional (to be implemented...)

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Author Name: Borys Jurgiel (@borysiasty)

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Exactly. It's on very hign position on my TODO list, but I haven't touch it yet. I'll do my best to implement it in February.

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Author Name: Giovanni Manghi (@gioman)

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I would like also to see this feature implemented, not only because I think is useful, but also because -the missing of this tool- is one of that things that (other software) users do notice when using for the first time QGis.

[qgib]

Author Name: Horst Düster (@hdus)

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Replying to [comment:14 lutra]:

I would like also to see this feature implemented, not only because I think is useful, but also because -the missing of this tool- is one of that things that (other software) users do notice when using for the first time QGis.

+1

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Author Name: Martin Dobias (@wonder-sk)

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What operations and functions should such field calculator support?

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Author Name: Giovanni Manghi (@gioman)

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Replying to [comment:16 wonder]:

What operations and functions should such field calculator support?

I know that make comparisons it is always bad, but (if you want to stay out of the arc* playground) I would suggest to have a look at the "field calculator" of gvSIG. It has many commands, every one has his own short description, so you may want to have a look to the program (I cannot find references of all the commands, not even in the manual, pag. 220 [ftp://downloads.gvsig.org/gva/descargas/manuales/gvSIG-1_1-man-v1-en.pdf here]).

See the attached image.

Among the others you can calculate areas, perimeters and lenghts without having to create a new shapefile like ftools requires.

Command list:

ABS 
ACOS
AREA
ASIN
ATAN
CEIL
COS
< >
/
E
==
EXP
<=
<
LOG
MAX
MIN
-
>=
>
PERIMETER
PI
+
POW
RANDOM
ROUND
SIN
SSQRT
TAN
*
TODEGREES
TONUMBER
TORADIANS
TOSTRING

[qgib]

Author Name: Marco Hugentobler (@mhugent)

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Note: a field calculator is on my (implementation) roadmap for this summer.

Marco

[qgib]

Author Name: Marco Hugentobler (@mhugent)

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A field calculator is available from
59a486b (SVN r11736) on (more operators will follow)

Marco

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• status_id was changed from Open to Closed
• resolution was changed from to fixed