Re: [GRASS-user] Using r.resamp.stats for null values
katrin eggert wrote: > Just one question: is it possible to "count" number of cells with a certain > value (or nulls) from one scale that are being used to calculate each value > pixel of the target scale? Not directly, but you can create a binary (0/1 or null/1) version of the input map then use "r.resamp.stats method=sum ..." on that. -- Glynn Clements ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Using r.resamp.stats for null values
Just one question: is it possible to "count" number of cells with a certain value (or nulls) from one scale that are being used to calculate each value pixel of the target scale? Thanks 2011/6/22 Glynn Clements > > katrin eggert wrote: > > > I just one to confirm one thing. If I'm using r.resamp.stats with > > *mode *option. > > If the most frequent value is a null, will i have a null value in the > ouput? > > No. > > With the -n option, the output is null if any input cell is null. > Without the -n option, most aggregates (including "mode") ignore null > cells; you'll only get a null result if all input cells are null. > > IIRC, the only reason that nulls are retained in the array passed to > the aggregate functions is that some of them (e.g. interspersion, > regression) consider the cell's position within the array, and having > the caller discard nulls beforehand would interfere with this. > > -- > Glynn Clements > ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Using r.resamp.stats for null values
katrin eggert wrote: > I just one to confirm one thing. If I'm using r.resamp.stats with > *mode *option. > If the most frequent value is a null, will i have a null value in the ouput? No. With the -n option, the output is null if any input cell is null. Without the -n option, most aggregates (including "mode") ignore null cells; you'll only get a null result if all input cells are null. IIRC, the only reason that nulls are retained in the array passed to the aggregate functions is that some of them (e.g. interspersion, regression) consider the cell's position within the array, and having the caller discard nulls beforehand would interfere with this. -- Glynn Clements ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Using r.resamp.stats for null values
Hi there I just one to confirm one thing. If I'm using r.resamp.stats with *mode *option. If the most frequent value is a null, will i have a null value in the ouput? Thank you Kat ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Using r.resamp.stats
Jenny Turner wrote: > I have one question regarding null values: I'm using r.resamp.stats with > method average. My question is, if I have a Target pixel based on 10 null > values and 1 non-null value, the target pixel will be based only on valid > pixel? I mean, it only requires at least 1 value to produce an output value? Without -n, the aggregate is computed over the non-null values; if all values are null, the result will be null. With -n, if any value is null, the result will be null. -- Glynn Clements ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Using r.resamp.stats
I have one question regarding null values: I'm using r.resamp.stats with method average. My question is, if I have a Target pixel based on 10 null values and 1 non-null value, the target pixel will be based only on valid pixel? I mean, it only requires at least 1 value to produce an output value? Thanks Jenny ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] using r.resamp.stats- When I reach a tie
António Rocha wrote: > >> I'm planning on using r.resamp.stats in order to resample a grid to a > >> coarser resolution. Since I'm using this function with classes I will > >> use mode method (more frequentclass to fall into a destination cell is > >> the chosen). My question is: when I have a tie between two classes, how > >> does GRASS decides which class shall be chosen? > >> > > > > In the event of a tie, the lowest-numbered category is chosen. > > Thanks for your answer. Is there any other alternative, to resample > data, that uses another approach to solve tie events? What mechanism do you want? If you wanted e.g. the highest-numbered category, you could use r.mapcalc to create a map with the categories negated, run r.resamp.stats on that, then negate the result. Some other possibilities could reasonably be handled with a combination of pre- and post-processing. For others, the only practical solution is to modify lib/stats/c_mode.c. -- Glynn Clements ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] using r.resamp.stats- When I reach a tie
Hi Glynn. Thanks for your answer. Is there any other alternative, to resample data, that uses another approach to solve tie events? THanks Antonio Glynn Clements wrote: António Rocha wrote: I'm planning on using r.resamp.stats in order to resample a grid to a coarser resolution. Since I'm using this function with classes I will use mode method (more frequentclass to fall into a destination cell is the chosen). My question is: when I have a tie between two classes, how does GRASS decides which class shall be chosen? In the event of a tie, the lowest-numbered category is chosen. __ Information from ESET NOD32 Antivirus, version of virus signature database 5912 (20110227) __ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] using r.resamp.stats- When I reach a tie
António Rocha wrote: > I'm planning on using r.resamp.stats in order to resample a grid to a > coarser resolution. Since I'm using this function with classes I will > use mode method (more frequentclass to fall into a destination cell is > the chosen). My question is: when I have a tie between two classes, how > does GRASS decides which class shall be chosen? In the event of a tie, the lowest-numbered category is chosen. -- Glynn Clements ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] using r.resamp.stats- When I reach a tie
Greetings I'm planning on using r.resamp.stats in order to resample a grid to a coarser resolution. Since I'm using this function with classes I will use mode method (more frequentclass to fall into a destination cell is the chosen). My question is: when I have a tie between two classes, how does GRASS decides which class shall be chosen? Thanks Antonio __ Information from ESET NOD32 Antivirus, version of virus signature database 5906 (20110225) __ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
