Re: [Qgis-user] symbolize points by their size and category

[Alejandro Chamizo de Castro]

Thank you very much for your sopport.

Regards


[image: Mailtrack]

Remitente
notificado con
Mailtrack

12/02/19
8:36:32

El vie., 1 feb. 2019 a las 12:04, DelazJ () escribió:

> Hi,
>
> See
> https://docs.qgis.org/testing/en/docs/user_manual/working_with_vector/vector_properties.html#proportional-symbol-and-multivariate-analysis
>
> Regards,
> Harrissou
>
> Le ven. 1 févr. 2019 à 11:59, Raymond Nijssen  a
> écrit :
>
>> Hi Alejandro,
>>
>> You could do the color by a "categorized" symbol (as usual) and the size
>> based on a "data driven override" with an expression calculating your
>> attribute values to symbol sizes.
>>
>> Good luck,
>> Raymond
>>
>>
>> On 01-02-19 11:50, Alejandro Chamizo de Castro wrote:
>> > Hello colleagues,
>> >
>> > do you know if it is possible to symbolize in QGIS 3.x a layer of
>> points
>> > according to its size and its category?
>> > For example. size according to number and colors based on its category.
>> >
>> > Thank you
>> >
>> > --
>> > Alejandro Chamizo de Castro
>> > +34 653681823
>> > www.gisland.es 
>> >
>> >
>> > Mailtrack
>> > <
>> https://mailtrack.io?utm_source=gmail_medium=signature_campaign=signaturevirality5;>
>>
>> >   Remitente notificado con
>> > Mailtrack
>> > <
>> https://mailtrack.io?utm_source=gmail_medium=signature_campaign=signaturevirality5;>
>>
>> > 01/02/19 11:50:24
>> >
>> >
>> > ___
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[Qgis-user] OpenCL acceleration on Windows 10 and Nvidia

[Nicolas Cadieux]

Hi,

Has anyone been able to successfully enable OpenCL acceleration 
(Settings/Options/Acceleration/Enable OpenCL acceleration) with QGIS 
3.4.4, OSGeo4W64, Windows 10_64x, and a RTX2060, GTX 260 (or later) or 
with the Intel OpenCL runtime 18 for CPU?


So far, I have tried with a GTX260 nvidia card with latest drivers (That 
made Qgis crash). I then installed a RTX2060 card and RTX2060 drivers 
with and without CUDA toolkit, installed OpenCL runtime 18 for CPU.  GPU 
caps identifies both CPU Runtime (OpenCL 2.1) and nvidia GeForce 2060 
OpenCL 1.2 cuda.  QGIS cannot find any compatible devices.


If you have Windows 10 and a Nvidia card, please test.  The developer is 
having trouble with this configuration and I am trying to help him out.


Nicolas

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Re: [Qgis-user] Snapping in Qgis 3.4

[Alexandre Neto]

Hi Tony, can you explain a bit more. What are you trying (describe the
steps), and what do you mean by it's failing.

Alexandre Neto

A seg, 11/02/2019, 08:26, Anthony Greenish  escreveu:

> Hi
>
>
>
> I am having getting the snapping function to work or turn on when I am
> digitizing a vector in Qgis 3.4. Any help would be appreciated.
>
>
>
> Tony
>
>
>
>
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Re: [Qgis-user] Proportional Symbols Bug in 3.2?

[Nicolas Cadieux]

Perhaps your size field is stored in a text format and not a float or int 
format...
Look at your” Layer properties, information, Fields.”

> Le 11 févr. 2019 à 12:39, Aj Hollenbach  a écrit :
> 
> Hi QGIS User Community!
> 
> I am attempting to represent water utilities (points) using graduated symbols 
> (by size), and would like the symbols to be proportional to the number of 
> customers. I thought that this could be done be done under the symbology 
> dialogue box by selecting "graduated" and then "size" for the method while 
> also using the "data-defined size legend" option under the "advanced" 
> sub-menu. However, whenever I click on the "advanced" button and then select 
> "data-defined size legend", I receive an error message that "data-defined 
> size is not enabled". Is this a bug in version 3.2, or am I doing something 
> incorrectly? Alternatively, is there another approach creating proportional 
> symbols by size for point data?
> 
> Thanks Much,
> Allen
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[Qgis-user] Proportional Symbols Bug in 3.2?

[Aj Hollenbach]

 Hi QGIS User Community!

I am attempting to represent water utilities (points) using *graduated
symbols* (by size), and would like the symbols to be *proportional* to the
number of customers. I thought that this could be done be done under the
symbology dialogue box by selecting "graduated" and then "size" for the
method while also using the "*data-defined size legend*" option under the
"advanced" sub-menu. However, whenever I click on the "advanced" button and
then select "data-defined size legend", I receive an error message
that "*data-defined
size is not enabled*". Is this a bug in version 3.2, or am I doing
something incorrectly? Alternatively, is there another approach creating
proportional symbols by size for point data?

Thanks Much,
Allen
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[QGIS-it-user] QGIS 3.4.4 Poligonizzazione - da raster a vettore

[Totò]

Salve a tutti,
l'algoritmo in oggetto crea un vettore di output con un campo integer,
questo esclude tutti i casi in cui il raster ha valori con virgola.

Secondo voi è un bug da segnalare??

saluti



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[Qgis-user] qgis3 uses IE as default browser on windows10?

[Groene Bij]

Hi,

 

Is there a setting in qgis3 to change the default browser used by processes?

For instance, qgis2web opens a webbrowser after exporting the webmap. In
qgis2.18 my default browser Firefox was opened. Now, qgis3.4.4 it opens IE.

 

According to Tom Chadwin (qgis2web) the plugin refers to a piece of Pyhton
code when opening the webbrowser:

The code which opens the browser when you export is:

 

https://github.com/tomchadwin/qgis2web/blob/master/qgis2web/maindialog.py#L3
42

It uses the Python webbrowser module:

 
https://docs.python.org/3/library/webbrowser.html

 

I have no experience with pyhon, so I hope there is a setting somewhere to
choose my default browser. Besides that, I do hope qgis3 will simply follow
the default settings from the OS.

 

Kind regards.

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[QGIS-it-user] errore SAGA (via QGIS) - grid extent

[Daniele Bonaposta]

Ciao a tutti,
sto utilizzando l'algoritmo k-means di SAGA tramite QGIS. I vari raster che
entrano come input per questo algoritmo, provengono tutti dal medesimo DEM,
il quale è stato ottenuto da un "ritaglio" di un modello digitale molto più
esteso.
L'algoritmo non viene nemmeno eseguito ed indica: "Input layers do not have
the same grid extent".
Ho effettuato un controllo sugli extent ed ottengo:

dem  611242.8781000546878204  928886.57*00562233105302*  642496.4609887
*244878337*  95866*4.0876974593847990*
tpi 611242.8781000546878204  928886.5712754763662815
642496.4609887985279784  958660.4579813877353445
slope 611242.8781000546878204  928886.5712754763662815
642496.4609887985279784  958660.4579813877353445
profile 611242.8781000546878204  928886.5712754763662815
642496.4609887985279784  958660.4579813877353445
plan 611242.8781000546878204  928886.5712754763662815
642496.4609887985279784  958660.4579813877353445

Tutti i raster derivati dal dem hanno lo stesso identico extent, preciso
fino all'ultimo decimale.
Il dem, che è il padre di tutti gli altri, è leggermente diverso (ho
evidenziato le differenze).
Ho provato a far girare l'algoritmo senza  il dem e funziona alla
perfezione, evidentemente i parametri dell'extent del modello digitale sono
i responsabili dell'alert.

Come è possibile che ci sia questa differenza? Come posso correggere
l'extent del dem in modo tale da utilizzare dal k-means?

Saluti e grazie,
Daniele
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Re: [Qgis-user] nodata and raster calc

[Nicolas Cadieux]

Hi,
In 99 % of what I do, treating nodata in any other way than a data mask would 
be severely detrimental to my results.  This would include OR and AND. (The 
scientific equivalence of “Do you want it eat pizza or ‘I don’t know’? or Do 
you want to eat pizza or nothing?” are two different valid questions.

Data mask should be the default for simplicity with user being able to select 
other behaviours implemented.
Nicolas

> Le 11 févr. 2019 à 05:02,   a écrit :
> 
> In fact I would always expect nodata. nodata is what it says: no data. How 
> can one calculate or generate new values with one unknown term. Especially in 
> the case of boolean.
> Lets take an example from real life. You have the information of wet or not 
> wet area. In the case of wet you have to reduce irrigation if not wet you 
> must increase irrigation. In either cases you make a mistake, if you do the 
> opposite. Without knowledge of the inputdata (and respecting the scale), 
> someone getting the result could do a big mistake. Particularly if the action 
> is highly cost intensive. Nodata need special treatment. One must be aware of 
> the lack of data, and a model has rather to fail than false simulate the 
> existing data. What if you process hundreds of raster sets and get always 
> valid results. If some don't like nodata, he has to actively process the data 
> in one way, either simulate valid data (and of course knows that he has to 
> communicate that fact) or collect more precise data. Anything else is 
> scientifically bad behaviour (to use a buzzword: fake data).
> 
> Cheers.
> 
> Stefan
> 
>> Havard Tveite  hat am 11. Februar 2019 um 10:20 
>> geschrieben:
>> 
>> 
>> nodata + 1 = nodata
>> nodata * 1 = nodata
>> nodata AND 1 = nodata
>> nodata OR 1 = 1
>> 
>> nodata + 0 = nodata
>> nodata * 0 = nodata
>> nodata AND 0 = 0
>> nodata OR 0 = nodata
>> 
>> Håvard
>> 
>>> On 11. feb. 2019 09:47, st_kie...@web.de wrote:
>>> I absolutely agree.
>>> 
>>> For the Discussion. nodata is a valuable information, and is getting lost 
>>> when dealing as desired value. Although the OR part needs more Discussion. 
>>> For consistency that has to be nodata as well.  What about nodata OR 0? In 
>>> my opinion nodata always needs a discrete treatment to avoid generating 
>>> fallcious information.
>>> 
>>> Cheers
>>> 
>>> Stefan
>>> 
 Havard Tveite  hat am 11. Februar 2019 um 09:38 
 geschrieben:
 
 
 nodata + 1 = nodata
 nodata * 1 = nodata
 nodata AND 1 = nodata
 nodata OR 1 = 1
 
 Håvard
 
> On 11. feb. 2019 03:11, Nyall Dawson wrote:
> Hey all,
> 
> I'm seeking some feedback on whether our current handling of nodata
> pixels in the raster calculator is correct, or (my suspicion) annoying
> and limiting.
> 
> Current
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Re: [QGIS-it-user] QGIS 3 ...Fogli non Figli ;-)

[Marco Spaziani]

No, no, io lascerei così com'è guarda ...se ci sono arrivato io
(che, di comprendonio, sono più tosto del legno) a capire (anche se l'ho
capito in ritardo) che "Figli" si riferiva a un gerarchicamente più elevato
"Parent", vuol dire che lo può capire chiunque abbia il pollice opponibile
alle altre dita ;-)

Il giorno lun 11 feb 2019 alle ore 12:16 Martina Savarese <
martina.savar...@gmail.com> ha scritto:

> Credo di aver tradotto io i "termini incriminati" e ricordo di aver avuto
> molti dubbi in proposito. Ogni suggerimento è ben accetto cmq. Nello
> specifico poi ho usato la traduzione "genitore" per "parent" sia perché è
> quella corretta sia perché ci possono essere vari gruppi annidati uno nell'
> altro: con i sottogruppi abbiamo appunto questa parola, ma nel caso inverso
> mi suonava male "e tutti i sovragruppi". Che dite di "e tutti i suoi padri"
> ?
> ;)
> Martina
>
> Il giorno Lun 11 Feb 2019 08:58 Marco Spaziani 
> ha scritto:
>
>> ...ora che ci penso meglio ...mi sta sorgendo il dubbio che invece il
>> termine "Figli" (nel senso di sublayer costituenti un layer gruppo "padre"
>> o "madre" che dir si voglia) sia invece il termine corretto da usarsi
>> ...boh ...non lo so ...ma se il termine Figli fosse corretto,
>> effettivamente, ripensandoci, non lo troverei strano.
>>
>> Il giorno lun 11 feb 2019 alle ore 08:50 Marco Spaziani <
>> spaziani.ma...@gmail.com> ha scritto:
>>
>>> Segnalo che poco fa ho notato che creando un gruppo di layer e poi
>>> cliccando col tasto dx del mouse sul "layer gruppo" così creato, tra le
>>> varie voci del menu a tendina compare anche "Seleziona tutti i Figli" o
>>> "Deseleziona tutti i Figli". Niente di importante o di urgente però lo
>>> metterei nella lista delle cose da correggere.
>>>
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Re: [Qgis-user] QGIS 3.4.4 add ellipse

[Janneke van Dijk]

Ok, I have no idea what went wrong the first time - I just ended up with 
lots of graphics and no records in tables - but starting a new project, 
creating a new geopackage with regular polygon as geometry type the tool 
now works as I expected - geometries and records are added to the 
attribute table. Sorry for the noise. It's a great tool!

Janneke

On 11/02/2019 15:02, Janneke van Dijk wrote:

Dear list,

I just discovered that QGIS 3 has the nice option to add ellipses in 
the editing toolbar. Does this just add a graphic to the map? I was 
hoping I could add a polygon in the shape of an ellipse to a vector 
layer. I have tried both with a shape file (polygon) and with a 
geopackage (curved polygon). What I do:


1. activate the empty polygon layer

2. toggle editing

3. use add ellipse from extent - draw ellips

4. toggle editing - no question to save the edits, and no record added 
to the vector layer.


Is it not supposed to add a record to the layer?

Thanks for any help!

Janneke




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[Qgis-user] QGIS 3.4.4 add ellipse

[Janneke van Dijk]

Dear list,

I just discovered that QGIS 3 has the nice option to add ellipses in the 
editing toolbar. Does this just add a graphic to the map? I was hoping I 
could add a polygon in the shape of an ellipse to a vector layer. I have 
tried both with a shape file (polygon) and with a geopackage (curved 
polygon). What I do:


1. activate the empty polygon layer

2. toggle editing

3. use add ellipse from extent - draw ellips

4. toggle editing - no question to save the edits, and no record added 
to the vector layer.


Is it not supposed to add a record to the layer?

Thanks for any help!

Janneke


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Re: [Qgis-user] repair tabs on log messages

[Havard Tveite]

The tabs reappear when new log messages come in.
No need to restart QGIS.

Håvard

On 11. feb. 2019 11:55, Groene Bij wrote:

Hi,

Using qgis 3.4.4 and opening the log messages panel, I accidentally 
deleted one of the tabs, but I don’t know which one.


Do they automatically re-appear after restarting qgis?

Can I somewhere choose which tabs to be visible in the message log 
panel? Clicking the cross symbol removes the tab, but how to get it back?


Kind regards



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Re: [QGIS-it-user] QGIS 3 ...Fogli non Figli ;-)

[Martina Savarese]

Credo di aver tradotto io i "termini incriminati" e ricordo di aver avuto
molti dubbi in proposito. Ogni suggerimento è ben accetto cmq. Nello
specifico poi ho usato la traduzione "genitore" per "parent" sia perché è
quella corretta sia perché ci possono essere vari gruppi annidati uno nell'
altro: con i sottogruppi abbiamo appunto questa parola, ma nel caso inverso
mi suonava male "e tutti i sovragruppi". Che dite di "e tutti i suoi padri"
?
;)
Martina

Il giorno Lun 11 Feb 2019 08:58 Marco Spaziani 
ha scritto:

> ...ora che ci penso meglio ...mi sta sorgendo il dubbio che invece il
> termine "Figli" (nel senso di sublayer costituenti un layer gruppo "padre"
> o "madre" che dir si voglia) sia invece il termine corretto da usarsi
> ...boh ...non lo so ...ma se il termine Figli fosse corretto,
> effettivamente, ripensandoci, non lo troverei strano.
>
> Il giorno lun 11 feb 2019 alle ore 08:50 Marco Spaziani <
> spaziani.ma...@gmail.com> ha scritto:
>
>> Segnalo che poco fa ho notato che creando un gruppo di layer e poi
>> cliccando col tasto dx del mouse sul "layer gruppo" così creato, tra le
>> varie voci del menu a tendina compare anche "Seleziona tutti i Figli" o
>> "Deseleziona tutti i Figli". Niente di importante o di urgente però lo
>> metterei nella lista delle cose da correggere.
>>
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[Qgis-user] repair tabs on log messages

[Groene Bij]

Hi,

 

Using qgis 3.4.4 and opening the log messages panel, I accidentally deleted
one of the tabs, but I don't know which one.

Do they automatically re-appear after restarting qgis?

Can I somewhere choose which tabs to be visible in the message log panel?
Clicking the cross symbol removes the tab, but how to get it back?

 

Kind regards

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Re: [Qgis-user] nodata and raster calc

[st_kiefer]

In fact I would always expect nodata. nodata is what it says: no data. How can 
one calculate or generate new values with one unknown term. Especially in the 
case of boolean.
Lets take an example from real life. You have the information of wet or not wet 
area. In the case of wet you have to reduce irrigation if not wet you must 
increase irrigation. In either cases you make a mistake, if you do the 
opposite. Without knowledge of the inputdata (and respecting the scale), 
someone getting the result could do a big mistake. Particularly if the action 
is highly cost intensive. Nodata need special treatment. One must be aware of 
the lack of data, and a model has rather to fail than false simulate the 
existing data. What if you process hundreds of raster sets and get always valid 
results. If some don't like nodata, he has to actively process the data in one 
way, either simulate valid data (and of course knows that he has to communicate 
that fact) or collect more precise data. Anything else is scientifically bad 
behaviour (to use a buzzword: fake data).

Cheers.

Stefan

> Havard Tveite  hat am 11. Februar 2019 um 10:20 
> geschrieben:
> 
> 
> nodata + 1 = nodata
> nodata * 1 = nodata
> nodata AND 1 = nodata
> nodata OR 1 = 1
> 
> nodata + 0 = nodata
> nodata * 0 = nodata
> nodata AND 0 = 0
> nodata OR 0 = nodata
> 
> Håvard
> 
> On 11. feb. 2019 09:47, st_kie...@web.de wrote:
> > I absolutely agree.
> > 
> > For the Discussion. nodata is a valuable information, and is getting lost 
> > when dealing as desired value. Although the OR part needs more Discussion. 
> > For consistency that has to be nodata as well.  What about nodata OR 0? In 
> > my opinion nodata always needs a discrete treatment to avoid generating 
> > fallcious information.
> > 
> > Cheers
> > 
> > Stefan
> > 
> >> Havard Tveite  hat am 11. Februar 2019 um 09:38 
> >> geschrieben:
> >>
> >>
> >> nodata + 1 = nodata
> >> nodata * 1 = nodata
> >> nodata AND 1 = nodata
> >> nodata OR 1 = 1
> >>
> >> Håvard
> >>
> >> On 11. feb. 2019 03:11, Nyall Dawson wrote:
> >>> Hey all,
> >>>
> >>> I'm seeking some feedback on whether our current handling of nodata
> >>> pixels in the raster calculator is correct, or (my suspicion) annoying
> >>> and limiting.
> >>>
> >>> Currently, we treat nodata pixels the same as a "NULL" value in SQL --
> >>> so ANY function or operation with nodata as an input results in a
> >>> nodata output.
> >>>
> >>> This means:
> >>>
> >>> - nodata + 1 = nodata
> >>> - nodata * 1 = nodata
> >>> - nodata AND 1 = nodata
> >>> - nodata OR 1 = nodata
> >>>
> >>> To me this is a mistake. I don't think we should treat nodata the same
> >>> as NULL, and I think for rasters then "nodata OR 1" should return 1.
> >>>
> >>> The end result of the current behaviour is that ANY nodata input
> >>> blocks processing of that pixel. So you can't do something like take
> >>> two raster files, and create an output showing where either input has
> >>> a 1 value (which I would expect raster1@1 OR raster2@1 to do).
> >>>
> >>> Otherwise, we need to have some concept of "coalesce" in the raster
> >>> calc. So then at least you could do:
> >>>
> >>>   coalesce(raster1@1, 0) OR coalesce(raster@1, 0) 
> >>>
> >>>
> >>> Thoughts?
> >>>
> >>> Nyall
> >>> ___
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Re: [Qgis-user] nodata and raster calc

[Havard Tveite]

nodata + 1 = nodata
nodata * 1 = nodata
nodata AND 1 = nodata
nodata OR 1 = 1

nodata + 0 = nodata
nodata * 0 = nodata
nodata AND 0 = 0
nodata OR 0 = nodata

Håvard

On 11. feb. 2019 09:47, st_kie...@web.de wrote:

I absolutely agree.

For the Discussion. nodata is a valuable information, and is getting lost when 
dealing as desired value. Although the OR part needs more Discussion. For 
consistency that has to be nodata as well.  What about nodata OR 0? In my 
opinion nodata always needs a discrete treatment to avoid generating fallcious 
information.

Cheers

Stefan


Havard Tveite  hat am 11. Februar 2019 um 09:38 
geschrieben:


nodata + 1 = nodata
nodata * 1 = nodata
nodata AND 1 = nodata
nodata OR 1 = 1

Håvard

On 11. feb. 2019 03:11, Nyall Dawson wrote:

Hey all,

I'm seeking some feedback on whether our current handling of nodata
pixels in the raster calculator is correct, or (my suspicion) annoying
and limiting.

Currently, we treat nodata pixels the same as a "NULL" value in SQL --
so ANY function or operation with nodata as an input results in a
nodata output.

This means:

- nodata + 1 = nodata
- nodata * 1 = nodata
- nodata AND 1 = nodata
- nodata OR 1 = nodata

To me this is a mistake. I don't think we should treat nodata the same
as NULL, and I think for rasters then "nodata OR 1" should return 1.

The end result of the current behaviour is that ANY nodata input
blocks processing of that pixel. So you can't do something like take
two raster files, and create an output showing where either input has
a 1 value (which I would expect raster1@1 OR raster2@1 to do).

Otherwise, we need to have some concept of "coalesce" in the raster
calc. So then at least you could do:

  coalesce(raster1@1, 0) OR coalesce(raster@1, 0) 


Thoughts?

Nyall
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Re: [Qgis-user] nodata and raster calc

[st_kiefer]

I absolutely agree.

For the Discussion. nodata is a valuable information, and is getting lost when 
dealing as desired value. Although the OR part needs more Discussion. For 
consistency that has to be nodata as well.  What about nodata OR 0? In my 
opinion nodata always needs a discrete treatment to avoid generating fallcious 
information.

Cheers

Stefan

> Havard Tveite  hat am 11. Februar 2019 um 09:38 
> geschrieben:
> 
> 
> nodata + 1 = nodata
> nodata * 1 = nodata
> nodata AND 1 = nodata
> nodata OR 1 = 1
> 
> Håvard
> 
> On 11. feb. 2019 03:11, Nyall Dawson wrote:
> > Hey all,
> > 
> > I'm seeking some feedback on whether our current handling of nodata
> > pixels in the raster calculator is correct, or (my suspicion) annoying
> > and limiting.
> > 
> > Currently, we treat nodata pixels the same as a "NULL" value in SQL --
> > so ANY function or operation with nodata as an input results in a
> > nodata output.
> > 
> > This means:
> > 
> > - nodata + 1 = nodata
> > - nodata * 1 = nodata
> > - nodata AND 1 = nodata
> > - nodata OR 1 = nodata
> > 
> > To me this is a mistake. I don't think we should treat nodata the same
> > as NULL, and I think for rasters then "nodata OR 1" should return 1.
> > 
> > The end result of the current behaviour is that ANY nodata input
> > blocks processing of that pixel. So you can't do something like take
> > two raster files, and create an output showing where either input has
> > a 1 value (which I would expect raster1@1 OR raster2@1 to do).
> > 
> > Otherwise, we need to have some concept of "coalesce" in the raster
> > calc. So then at least you could do:
> > 
> >  coalesce(raster1@1, 0) OR coalesce(raster@1, 0) 
> > 
> > 
> > Thoughts?
> > 
> > Nyall
> > ___
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> > Qgis-user@lists.osgeo.org
> > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
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Re: [Qgis-user] nodata and raster calc

[Micha Silver]

  
  

On 11/02/2019 10:42, Tim Sutton wrote:


  
  Hi
  

  On 11 Feb 2019, at 10:38, Havard Tveite 
wrote:
  
  nodata + 1 = nodata
nodata * 1 = nodata
nodata AND 1 = nodata
nodata OR 1 = 1
  



  



It might be worth noting that in the GRASS mapcalc module,
  there's a special operator for these situations. From the manpage:

  NULL-values in any arithmetic or logical operation should
result
in NULL. (however, &&& and ||| are treated
specially, as described below).
  
  The &&& and ||| operators observe the following
axioms even when x is NULL:

  	x &&& false == false
	false &&& x == false
	x ||| true == true
	true ||| x == true


  


  


Hmm yes, the OR case should return one!


Regards


Tim


  
  
  
 
  

  
  
  
  ---


Tim Sutton
t...@qgis.org


  
  
  

  
  
  
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-- 
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
+972-523-665918
  

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Re: [Qgis-user] nodata and raster calc

[Stefan Giese]

I've thought that AND and OR are boolean operators and will produce TRUE 
(1) or FALSE (0)


nodata + 1 = nodata
nodata * 1 = nodata
nodata AND 1 = 0 (false)
nodata OR 1 = 1 (true)

Mit freundlichen Grüßen
Stefan Giese
Projektleiter/Consultant

FOSS Academy Kompaktkurs "Winterschule 2019"
Grundwissen zum Aufbau von Geodateninfrastrukturen mit Open-Source-Software
https://foss-academy.com/kompaktkurse

WhereGroup GmbH & Co. KG
Schwimmbadstr. 2
79100 Freiburg
Germany

Fon: +49 (0)761 / 519 102 - 61
Fax: +49 (0)761 / 519 102 - 11

stefan.gi...@wheregroup.com
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Amtsgericht Bonn, HRA 6788
---
Komplementärin:
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vertreten durch:
Olaf Knopp, Peter Stamm
---

Am 11.02.2019 um 09:38 schrieb Havard Tveite:

nodata + 1 = nodata
nodata * 1 = nodata
nodata AND 1 = nodata
nodata OR 1 = 1

Håvard

On 11. feb. 2019 03:11, Nyall Dawson wrote:

Hey all,

I'm seeking some feedback on whether our current handling of nodata
pixels in the raster calculator is correct, or (my suspicion) annoying
and limiting.

Currently, we treat nodata pixels the same as a "NULL" value in SQL --
so ANY function or operation with nodata as an input results in a
nodata output.

This means:

- nodata + 1 = nodata
- nodata * 1 = nodata
- nodata AND 1 = nodata
- nodata OR 1 = nodata

To me this is a mistake. I don't think we should treat nodata the same
as NULL, and I think for rasters then "nodata OR 1" should return 1.

The end result of the current behaviour is that ANY nodata input
blocks processing of that pixel. So you can't do something like take
two raster files, and create an output showing where either input has
a 1 value (which I would expect raster1@1 OR raster2@1 to do).

Otherwise, we need to have some concept of "coalesce" in the raster
calc. So then at least you could do:

 coalesce(raster1@1, 0) OR coalesce(raster@1, 0) 


Thoughts?

Nyall
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Re: [Qgis-user] nodata and raster calc

[Tim Sutton]

Hi

> On 11 Feb 2019, at 10:38, Havard Tveite  wrote:
> 
> nodata + 1 = nodata
> nodata * 1 = nodata
> nodata AND 1 = nodata
> nodata OR 1 = 1


Hmm yes, the OR case should return one!

Regards

Tim


 




---

Tim Sutton
t...@qgis.org




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Re: [Qgis-user] nodata and raster calc

[Havard Tveite]

nodata + 1 = nodata
nodata * 1 = nodata
nodata AND 1 = nodata
nodata OR 1 = 1

Håvard

On 11. feb. 2019 03:11, Nyall Dawson wrote:

Hey all,

I'm seeking some feedback on whether our current handling of nodata
pixels in the raster calculator is correct, or (my suspicion) annoying
and limiting.

Currently, we treat nodata pixels the same as a "NULL" value in SQL --
so ANY function or operation with nodata as an input results in a
nodata output.

This means:

- nodata + 1 = nodata
- nodata * 1 = nodata
- nodata AND 1 = nodata
- nodata OR 1 = nodata

To me this is a mistake. I don't think we should treat nodata the same
as NULL, and I think for rasters then "nodata OR 1" should return 1.

The end result of the current behaviour is that ANY nodata input
blocks processing of that pixel. So you can't do something like take
two raster files, and create an output showing where either input has
a 1 value (which I would expect raster1@1 OR raster2@1 to do).

Otherwise, we need to have some concept of "coalesce" in the raster
calc. So then at least you could do:

 coalesce(raster1@1, 0) OR coalesce(raster@1, 0) 


Thoughts?

Nyall
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[Qgis-user] Snapping in Qgis 3.4

[Anthony Greenish]

Hi

 

I am having getting the snapping function to work or turn on when I am
digitizing a vector in Qgis 3.4. Any help would be appreciated.

 

Tony

 

 

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