Reclassify by layer/table

[qgib]

Author Name: Henk Thoma (Henk Thoma)
Original Redmine Issue: 21263

Redmine category:map_tools

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The current Reclassify by layer tool requires a vector layer (with geometry info) to select table fields for minimum, maximum & values. It doesn't work with a standalone table (e.g. one imported from Excel or CSV).
In the new Reclassify by table tool one has to manually provide the table values. It could be upgraded by providing an input for a standalone table as well.

[baswein]

In QGIS 3.6 I have been using both Excel and CSV files in the Reclassify by Layer tool. I have found that it is a little sensitive. For example with CSV I can't have field names in the table. With excel I can have names but sometimes I need to save it as a CSV open it up with a text editor delete any extra blank rows at the bottom and then resave it as an excel. I have also found I can save the excel as a shapefile even without geometry and use the .dbf file as the layer or save it to a geopackage and load the layer from there. Unless I am confusing the situation this is already a feature but the naming and is confusing.

[nyalldawson]

Is this still an issue? I can't reproduce

[baswein]

I'll check later today. At this point I have a model set up that works around it so haven't encountered it lately.

[baswein]

@nyalldawson It seems to be working with an excel file but not a CSV.
Here is a screenshot of the table.

Here is a gif of it working with an excel file.

Here not working with a CSV.

I tried removing the header of the csv and cleaning it up in a text editor and that didn't help. I also tried to add it to the layer panel and connect to it through that ans that didn't work.

QGIS version
3.12.2-București
QGIS code revision
8a1fb33
Compiled against Qt
5.11.2
Running against Qt
5.11.2
Compiled against GDAL/OGR
3.0.4
Running against GDAL/OGR
3.0.4
Compiled against GEOS
3.8.1-CAPI-1.13.3
Running against GEOS
3.8.1-CAPI-1.13.3
Compiled against SQLite
3.29.0
Running against SQLite
3.29.0
PostgreSQL Client Version
11.5
SpatiaLite Version
4.3.0
QWT Version
6.1.3
QScintilla2 Version
2.10.8
Compiled against PROJ
6.3.1
Running against PROJ
Rel. 6.3.2, May 1st, 2020
OS Version
Windows 10 (10.0)
Active python plugins
db_manager;
MetaSearch;
processing

[nyalldawson]

Right -- I suspect that's because the csv has imported those columns as a text column, and the dialog is only allowing choices of numeric columns.

Try opening your dataset through the Data Source Manager -> Delimited Text option. That should automatically detect that the column is numeric and avoid the forced string conversion.

[baswein]

That works and makes sense. So the excel file has more info and it can parse it. If I remember right
I originally noticed it when using it through graphical modeler (that's always a tongue twister) where I was using the csv I generated as a new input and i had to work around it.
Could Detect field types be turned on for all ways you can import a csv? For example today I created a csv using Raster layer zonal statistics with the csv automatically added to the map and the zones 1-22 came in as text. If so should I add that as a feature request? I was pleasantly surprised that QGIS could join fields even if they were different types. This is always an issue with my students in ArcMAP. Thanks again

[nyalldawson]

Right - the graphical modeler doesn't currently offer an easy way to import CSV data and perform the column type autodetection.

To do that we need a new "import delimited text" algorithm in processing which exposes all the nice options that you see in the dialog...