Re: [Qgis-user] Raster Calculator - If statements
Hi Jonathan:
As I said, this works band by band... so I think maybe you would can do:
ZERO For Band 1 : (band1@1<=145 and band2@1<=145 and band3@1<=145)*band1@1
ZERO For Band 2 : (band1@1<=145 and band2@1<=145 and band3@1<=145)*band2@1
ZERO For Band 3 : (band1@1<=145 and band2@1<=145 and band3@1<=145)*band3@1
NULL For Band 1 : ( ((band1@1<=145 and band2@1<=145 and band3@1<=145)*band1@1)
/ ((band1@1<=145 and band2@1<=145 and band3@1<=145)*band1@1) ) * band1@1
NULL For Band 2 : ( ((band1@1<=145 and band2@1<=145 and band3@1<=145)*band2@1)
/ ((band1@1<=145 and band2@1<=145 and band3@1<=145)*band2@1) ) * band2@1
NULL For Band 3 : ( ((band1@1<=145 and band2@1<=145 and band3@1<=145)*band3@1)
/ ((band1@1<=145 and band2@1<=145 and band3@1<=145)*band3@1) ) * band3@1
After that, you'll must have to merge this bands (Raster-->Miscellany -->
Merge )
Good Luck
Carlos
2014-02-24 9:30 GMT-05:00 Jonathan Moules <
jonathanmou...@warwickshire.gov.uk>:
> Hi Carlos,
> Thanks for your thoughts. One observation - it appears that you are only
> checking a single band at a time.
> However I only want the values to be changed if ALL bands have a value of
> >145. If only one or even two of the values are >145 then nothing should be
> changed, it's only when all three are that I want it to be triggered.
>
> That makes the problem even more tricky. :-)
> Kind Regards,
> Jonathan
>
>
>
> On 21 February 2014 21:40, Carlos Cerdán wrote:
>
>> Hi Jonathan:
>>
>> Interesting puzzle. You can get what you wish if you use GRASS (r.mapcalc
>> and r.null). With QGIS I just got zero or null, but band by band:
>>
>> ZERO : (band1@1<=145)*band1@1
>>
>> NULL : ( ((band1@1<=145)*band1@1) / ((band1@1<=145)*band1@1) ) * band1@1
>>
>> Explanation:
>>
>> 1. ZERO: When condition in parenthesis is true, it goes 1, if doesn't, 0.
>> After that, multiply by the same band, so result is 0 in cells that
>> original value was major than 145, and it's the same value as original in
>> other cells.
>>
>> 2. NULL: We have same prior value divided by himself. In cells where we
>> got 0, now will get NULL, and the original value in other cells.
>>
>> I used 145 according your example.
>>
>> Good luck
>>
>> Carlos
>>
>>
>>
>> 2014-02-21 8:37 GMT-05:00 Jonathan Moules <
>> jonathanmou...@warwickshire.gov.uk>:
>>
>>> Hi List,
>>> I have a three band raster. I want to do the following with:
>>>
>>> If (Band1 > 150 AND Band2 > 150 AND Band3 > 150){
Band1 = 255
Band1 = 255
Band1 = 255
}
>>>
>>>
>>> Basically set all band values to 255 when all band values are > than a
>>> value of 150. All other band values should remain unchanged.
>>>
>>> How do I do this? I've got as far as the below for the :
>>>
( "CR0569TEI_8_modified@1" > 145 AND "CR0569TEI_8_modified@2"
> 145 AND "CR0569TEI_8_modified@3" > 145 )
>>>
>>>
>>> But am unsure what's next. The tutorials I've found online assume I only
>>> want 1 or 0 as my results.
>>>
>>> Help welcome. :-)
>>> Thanks,
>>> Jonathan
>>>
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>>
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>
>
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Re: [Qgis-user] Raster Calculator - If statements
Hi Carlos,
Thanks for your thoughts. One observation - it appears that you are only
checking a single band at a time.
However I only want the values to be changed if ALL bands have a value of
>145. If only one or even two of the values are >145 then nothing should be
changed, it's only when all three are that I want it to be triggered.
That makes the problem even more tricky. :-)
Kind Regards,
Jonathan
On 21 February 2014 21:40, Carlos Cerdán wrote:
> Hi Jonathan:
>
> Interesting puzzle. You can get what you wish if you use GRASS (r.mapcalc
> and r.null). With QGIS I just got zero or null, but band by band:
>
> ZERO : (band1@1<=145)*band1@1
>
> NULL : ( ((band1@1<=145)*band1@1) / ((band1@1<=145)*band1@1) ) * band1@1
>
> Explanation:
>
> 1. ZERO: When condition in parenthesis is true, it goes 1, if doesn't, 0.
> After that, multiply by the same band, so result is 0 in cells that
> original value was major than 145, and it's the same value as original in
> other cells.
>
> 2. NULL: We have same prior value divided by himself. In cells where we
> got 0, now will get NULL, and the original value in other cells.
>
> I used 145 according your example.
>
> Good luck
>
> Carlos
>
>
>
> 2014-02-21 8:37 GMT-05:00 Jonathan Moules <
> jonathanmou...@warwickshire.gov.uk>:
>
>> Hi List,
>> I have a three band raster. I want to do the following with:
>>
>> If (Band1 > 150 AND Band2 > 150 AND Band3 > 150){
>>> Band1 = 255
>>> Band1 = 255
>>> Band1 = 255
>>> }
>>
>>
>> Basically set all band values to 255 when all band values are > than a
>> value of 150. All other band values should remain unchanged.
>>
>> How do I do this? I've got as far as the below for the :
>>
>>> ( "CR0569TEI_8_modified@1" > 145 AND "CR0569TEI_8_modified@2"
>>> > 145 AND "CR0569TEI_8_modified@3" > 145 )
>>
>>
>> But am unsure what's next. The tutorials I've found online assume I only
>> want 1 or 0 as my results.
>>
>> Help welcome. :-)
>> Thanks,
>> Jonathan
>>
>> This transmission is intended for the named addressee(s) only and may
>> contain sensitive or protectively marked material up to RESTRICTED and
>> should be handled accordingly. Unless you are the named addressee (or
>> authorised to receive it for the addressee) you may not copy or use it, or
>> disclose it to anyone else. If you have received this transmission in error
>> please notify the sender immediately. All email traffic sent to or from us,
>> including without limitation all GCSX traffic, may be subject to recording
>> and/or monitoring in accordance with relevant legislation.
>> ___
>> Qgis-user mailing list
>> Qgis-user@lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/qgis-user
>>
>
>
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contain sensitive or protectively marked material up to RESTRICTED and
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disclose it to anyone else. If you have received this transmission in error
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Re: [Qgis-user] Raster Calculator - If statements
Hi Jonathan:
Interesting puzzle. You can get what you wish if you use GRASS (r.mapcalc
and r.null). With QGIS I just got zero or null, but band by band:
ZERO : (band1@1<=145)*band1@1
NULL : ( ((band1@1<=145)*band1@1) / ((band1@1<=145)*band1@1) ) * band1@1
Explanation:
1. ZERO: When condition in parenthesis is true, it goes 1, if doesn't, 0.
After that, multiply by the same band, so result is 0 in cells that
original value was major than 145, and it's the same value as original in
other cells.
2. NULL: We have same prior value divided by himself. In cells where we
got 0, now will get NULL, and the original value in other cells.
I used 145 according your example.
Good luck
Carlos
2014-02-21 8:37 GMT-05:00 Jonathan Moules <
jonathanmou...@warwickshire.gov.uk>:
> Hi List,
> I have a three band raster. I want to do the following with:
>
> If (Band1 > 150 AND Band2 > 150 AND Band3 > 150){
>> Band1 = 255
>> Band1 = 255
>> Band1 = 255
>> }
>
>
> Basically set all band values to 255 when all band values are > than a
> value of 150. All other band values should remain unchanged.
>
> How do I do this? I've got as far as the below for the :
>
>> ( "CR0569TEI_8_modified@1" > 145 AND "CR0569TEI_8_modified@2" >
>> 145 AND "CR0569TEI_8_modified@3" > 145 )
>
>
> But am unsure what's next. The tutorials I've found online assume I only
> want 1 or 0 as my results.
>
> Help welcome. :-)
> Thanks,
> Jonathan
>
> This transmission is intended for the named addressee(s) only and may
> contain sensitive or protectively marked material up to RESTRICTED and
> should be handled accordingly. Unless you are the named addressee (or
> authorised to receive it for the addressee) you may not copy or use it, or
> disclose it to anyone else. If you have received this transmission in error
> please notify the sender immediately. All email traffic sent to or from us,
> including without limitation all GCSX traffic, may be subject to recording
> and/or monitoring in accordance with relevant legislation.
> ___
> Qgis-user mailing list
> Qgis-user@lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-user
>
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