[Qgis-user] Using the ##passfilename tag for R script in Processing Toolbox

[Victor Olaya]

No, that's not the idea off ##passfilename, the idea is that, instead of
getting an R variable that is already a vector/raster layer, you get a
string with its filename, so you can use it in R as you like. This was
mainly done to allow the user to open a raster layer using a different
package, and not use a fixed one and provide the layer object directly. So,
if you declare a variable "mylayer" as vector layer, Processing will ask
the user to select a vector layer, but the "mylayer" variable will have the
path to the selected file. If you do not use ##passfilename, Processing
will add some extra code, so the variable will already point to a data
object created based on that filename.

You can update to the newer version using the plugin manager. You should
enable the "show experimental plugins" option, and you will see a new
version of Processing.

To make feature requests, you can use the QGIS issue tracker.

Thanks in advance!


2014-02-11 22:51 GMT+01:00 Ned Horning <horning at amnh.org>:

>  Hi Victor -
>
> Yes, I am using the version of Processing that comes with QGIS 2.0.1.
>
> I played with it some more today and I don't get an error if I use
> ##passfilenames (I added an "s" at the end) but it still didn't seem to
> work. I'm assuming that using ##passfilename will simply declare the
> directory path and file name as a variable instead of actually opening the
> file. It's quite possible I don't understand the intended functionality.
>
> Can you let me know the best way to make comments or make feature requests
> related to the R scripting capability. I'm glad I finally got around to
> trying it out.
>
> All the best,
>
> Ned
>
>
> On 02/11/2014 04:41 PM, Victor Olaya wrote:
>
> Hi Ned
>
>  That looks like a bug when parsing the script code. I will check to see
> what I can do.
>
>  Are you using the latest version of Processing, or the one that comes
> with QGIS 2.0.1?
>
>
> 2014-02-10 23:03 GMT+01:00 Ned Horning <horning at amnh.org>:
>
>> Hi -
>>
>> I am trying to learn to write R scripts using the Processing Toolbox. I
>> have a random forest image classification script that works in the
>> processing toolkit but I'd like to modify it to do more complex tasks. I
>> think I need to use the ##passfilename tag but every time I add that to a
>> script I get an error that I pasted below. I tried several different
>> scripts and every time I add the ##passfilename tag I get the same error.
>> Does the ##passfilename tag  need other parameters? If anyone knows what
>> the problem might be or has pointers about how I can find the problem
>> please let me know?
>>
>> This R scripting capability has a lot of potential and I'd like to write
>> a guide on how to use it but I still have a lot to learn myself.
>>
>> All the best,
>>
>> Ned
>>
>>
>> I'm running QGIS 2.0.1 on Ubuntu 12.04. This is the error message:
>> --
>> An error has occured while executing Python code:
>>
>> Traceback (most recent call last):
>>   File
>> "/usr/share/qgis/python/plugins/processing/r/EditRScriptDialog.py", line
>> 95, in runAlgorithm
>>     alg = RAlgorithm(None, unicode(self.text.text()))
>>   File "/usr/share/qgis/python/plugins/processing/r/RAlgorithm.py", line
>> 71, in __init__
>>     self.defineCharacteristicsFromScript()
>>   File "/usr/share/qgis/python/plugins/processing/r/RAlgorithm.py", line
>> 82, in defineCharacteristicsFromScript
>>     self.parseDescription(iter(lines))
>>   File "/usr/share/qgis/python/plugins/processing/r/RAlgorithm.py", line
>> 108, in parseDescription
>>     raise WrongScriptException("Could not load R script:" +
>> self.descriptionFile + ".\n Problem with line \"" + line + "\"")
>> TypeError: cannot concatenate 'str' and 'NoneType' objects
>>
>> Python version:
>> 2.7.3 (default, Sep 26 2013, 20:13:52)
>> [GCC 4.6.3]
>>
>>
>> QGIS version:
>> 2.0.1-Dufour Dufour, exported
>>
>> Python path: ['/usr/share/qgis/python/plugins/processing',
>> '/usr/share/qgis/python', '/home/nedhorning/.qgis2/python',
>> '/home/nedhorning/.qgis2/python/plugins', '/usr/share/qgis/python/plugins',
>> '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2',
>> '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old',
>> '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages',
>> '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL',
>> '/usr/lib/python2.7/dist-packages/gst-0.10',
>> '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/pymodules/python2.7',
>> '/usr/lib/python2.7/dist-packages/ubuntu-sso-client',
>> '/usr/lib/python2.7/dist-packages/ubuntuone-client',
>> '/usr/lib/python2.7/dist-packages/ubuntuone-installer',
>> '/usr/lib/python2.7/dist-packages/ubuntuone-storage-protocol',
>> '/usr/lib/python2.7/dist-packages/wx-2.8-gtk2-unicode',
>> '/usr/share/qgis/python/plugins/fTools/tools']
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>
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