[R] Classification of wind events
Jeff Newmiller
jdnewm|| @end|ng |rom dcn@d@v|@@c@@u@
Mon May 18 17:21:42 CEST 2020
While I can understand that such techniques might not seem obvious at first, they are building blocks that you should be able to use to solve similar problems in the future. Don't give up because it surprised you this time, and do play with modifying it to better understand this time.
Replace code starting with calculation of foehn1d:
# calculate mean values by candidate group
mydf$foehn1c2 <- ave( mydf$max_speed
, mydf$foehn1b
, FUN=mean
)
# find starts of foehns
mydf$foehn1d <- with( mydf
, 0 < diff( c( 0, foehn1c & 8<foehn1c2 ) )
)
# identify foehns distinctly (multiple days)
mydf$foehn1e <- with( mydf
, ifelse( foehn1c
, cumsum( foehn1d )
, 0
)
)
mydf[ , c( "data_POSIX" , "main_dir", "max_speed" , "foehn1e" ) ]
On May 18, 2020 3:14:06 AM PDT, Stefano Sofia <stefano.sofia using regione.marche.it> wrote:
>Sorry for my fault.
>I am very grateful for such code, which is extremely efficient. I would
>have never been able to reach these results.
>
>In order to preserve the quality of this code, I dare to ask you a
>final question: once identified each single period in the column
>foehn1c, this period can be taken into consideration only if within it
>the mean of max_speed is higher than 8.0 (which is speed in m/s).
>Could you please help me in this final step?
>
>Thank you again for all your help
>Stefano
>
>
> (oo)
>--oOO--( )--OOo----------------
>Stefano Sofia PhD
>Civil Protection - Marche Region
>Meteo Section
>Snow Section
>Via del Colle Ameno 5
>60126 Torrette di Ancona, Ancona
>Uff: 071 806 7743
>E-mail: stefano.sofia using regione.marche.it
>---Oo---------oO----------------
>
>________________________________________
>Da: Jeff Newmiller [jdnewmil using dcn.davis.ca.us]
>Inviato: sabato 16 maggio 2020 21.04
>A: Stefano Sofia; Jim Lemon; r-help mailing list
>Oggetto: RE: [R] Classification of wind events
>
>Please run your code before posting it... you forgot the quotes in your
>main_dir column.
>
>first_day_POSIX <- as.POSIXct("2020-02-19-00-00",
>format="%Y-%m-%d-%H-%M")
>last_day_POSIX <- as.POSIXct("2020-02-20-00-00",
>format="%Y-%m-%d-%H-%M")
>mydf <- data.frame(data_POSIX=seq(first_day_POSIX, last_day_POSIX,
>by="10 min"))
>
>mydf$main_dir <- c("WSW", "WSW", "SW", "SW", "W", "WSW", "WSW", "WSW",
>"W", "W", "SW", "WSW", "SSW", "S", "SW", "SW", "WSW", "WNW", "W",
>"WSW", "WSW", "SE", "SE", "SE", "NW", "NNE", "ENE", "SE", "NNW", "NW",
>"NW", "NW", "NW", "NW", "NW", "NE", "NW", "NW", "NW", "NW", "NW", "N",
>"WNW", "NW", "NNW", "NNW", "NW", "NW", "NW", "WNW", "ESE", "W", "WSW",
>"SW", "SW", "SW", "WSW", "SW", "S", "S", "SSW", "SW", "WSW", "WSW",
>"WSW", "WSW", "WSW", "WSW", "WSW", "SW", "WSW", "WSW", "WSW", "WSW",
>"SW", "SW", "WSW", "WSW", "WSW", "WSW", "WSW", "SW", "SW", "SW", "SW",
>"SW", "SW", "SW", "SW", "SW", "WSW", "WSW", "WSW", "WSW", "SW", "SW",
>"SW", "SW", "WSW", "SW", "SW", "SW", "SW", "SW", "WSW", "SW", "SW",
>"W", "WSW", "WSW", "SSW", "S", "WNW", "SW", "W", "WSW", "WSW", "SE",
>"SE", "SE", "NW", "NNE", "ENE", "SE", "NNW", "NW", "NW", "NW", "NW",
>"NW", "NW", "NE", "NW", "NW", "NW", "NW", "NW", "N", "WNW", "NW",
>"NNW", "NNW", "NW", "NW", "NW")
>
>mydf$max_speed <- c(4.60, 4.60, 3.40, 3.10, 4.80, 4.20, 4.10, 4.50,
>4.70, 4.30, 2.40, 2.30, 2.20, 2.10, 2.90, 2.80, 1.80, 2.70, 4.30, 3.30,
>2.30, 2.30, 3.20, 3.20, 2.90, 2.30, 1.50, 1.80, 2.90, 2.40, 1.80, 2.40,
>2.30, 2.60, 1.80, 2.30, 1.90, 2.20, 2.80, 2.40, 1.00, 1.10, 1.60, 2.30,
>2.50, 3.30, 3.40, 3.20, 4.50, 3.90, 3.10, 2.40, 6.00, 7.80, 6.30, 7.80,
>8.10, 6.10, 7.40, 9.50, 8.90, 9.10, 10.10, 10.50, 11.10, 10.10, 10.90,
>11.30, 13.40, 13.50, 12.80, 11.50, 13.10, 13.50, 11.10, 10.50, 8.50,
>10.10, 10.70, 13.60, 11.90, 14.90, 10.90, 10.90, 12.80, 12.10, 9.10,
>8.30, 8.80, 7.40, 8.40, 10.30, 10.00, 7.00, 8.50, 8.40, 8.60, 6.70,
>7.30, 6.20, 5.90, 5.90, 5.10, 5.80, 5.60, 6.50, 6.60, 11.70, 11.30,
>8.70, 7.10, 6.90, 4.30, 3.80, 4.30, 3.30, 2.30, 2.30, 3.20, 3.20, 2.90,
>2.30, 1.50, 1.80, 2.90, 2.40, 1.80, 2.40, 2.30, 2.60, 1.80, 2.30, 1.90,
>2.20, 2.80, 2.40, 1.00, 1.10, 1.60, 2.30, 2.50, 3.30, 3.40, 3.20, 4.50)
># mark candidate rows
>mydf$foehn1a <- mydf$main_dir %in% c( "WSW", "SW" )
># mark unstable conditions
>mydf$foehn1b <- with( mydf
> , cumsum( !foehn1a )
> )
># find minimum length of foehn conditions
>mydf$foehn1c <- ave( rep( 1, nrow( mydf ) )
> , mydf$foehn1b
> , FUN=function(v) 10 < length( v )
> )
># find starts of foehns
>mydf$foehn1d <- with( mydf
> , 0 < diff( c( 0, foehn1c ) )
> )
># identify foehns distinctly (multiple days)
>mydf$foehn1e <- with( mydf
> , ifelse( foehn1c
> , cumsum( foehn1d )
> , 0
> )
> )
>mydf[ , c( 1, 2, 8 ) ]
>
>On May 16, 2020 3:21:24 AM PDT, Stefano Sofia
><stefano.sofia using regione.marche.it> wrote:
>>Dear Jim and Jeff,
>>thank you for your comments. You are right, it is quite difficult to
>>detect this process through a single observation point, I am awre of
>>it.
>>I need to set up an automatic algorithm to filter 20 years of data,
>and
>>I have to find an easy way to do it.
>>I know quite well my automatic stations, the wind direction is very
>>stable during these situations, and therefore I would like to start
>>from it. (I should use also wind speed, relative humidity and
>>temperature, but I will introduce them only once I will be able to
>>manage the direction).
>>In the case of the example below reported, I know that the directions
>>of this particular automatic station must be only SW or WSW.
>>
>>My biggest problem, obviously, is to find the beginning and the end of
>>each event, when there is a change in the main direction.
>>Thinking about categorical data in general, is there a way to detect
>>periods when one particular category is more frequent?
>>
>>Here I reproduce a real example 24 hours long, where these Foehn
>>condition start between 09 and 10 and finish after 19:
>>
>>first_day_POSIX <- as.POSIXct("2020-02-19-00-00",
>>format="%Y-%m-%d-%H-%M")
>>last_day_POSIX <- as.POSIXct("2020-02-20-00-00",
>>format="%Y-%m-%d-%H-%M")
>>mydf <- data.frame(data_POSIX=seq(first_day_POSIX, last_day_POSIX,
>>by="10 min"))
>>
>>mydf$main_dir <- c(WSW, WSW, SW, SW, W, WSW, WSW, WSW, W, W, SW, WSW,
>>SSW, S, SW, SW, WSW, WNW, W, WSW, WSW, SE, SE, SE, NW, NNE, ENE, SE,
>>NNW, NW, NW, NW, NW, NW, NW, NE, NW, NW, NW, NW, NW, N, WNW, NW, NNW,
>>NNW, NW, NW, NW, WNW, ESE, W, WSW, SW, SW, SW, WSW, SW, S, S, SSW, SW,
>>WSW, WSW, WSW, WSW, WSW, WSW, WSW, SW, WSW, WSW, WSW, WSW, SW, SW,
>WSW,
>>WSW, WSW, WSW, WSW, SW, SW, SW, SW, SW, SW, SW, SW, SW, WSW, WSW, WSW,
>>WSW, SW, SW, SW, SW, WSW, SW, SW, SW, SW, SW, WSW, SW, SW, W, WSW,
>WSW,
>>SSW, S, WNW, SW, W, WSW, WSW, SE, SE, SE, NW, NNE, ENE, SE, NNW, NW,
>>NW, NW, NW, NW, NW, NE, NW, NW, NW, NW, NW, N, WNW, NW, NNW, NNW, NW,
>>NW, NW)
>>
>>mydf$max_speed <- c(4.60, 4.60, 3.40, 3.10, 4.80, 4.20, 4.10, 4.50,
>>4.70, 4.30, 2.40, 2.30, 2.20, 2.10, 2.90, 2.80, 1.80, 2.70, 4.30,
>3.30,
>>2.30, 2.30, 3.20, 3.20, 2.90, 2.30, 1.50, 1.80, 2.90, 2.40, 1.80,
>2.40,
>>2.30, 2.60, 1.80, 2.30, 1.90, 2.20, 2.80, 2.40, 1.00, 1.10, 1.60,
>2.30,
>>2.50, 3.30, 3.40, 3.20, 4.50, 3.90, 3.10, 2.40, 6.00, 7.80, 6.30,
>7.80,
>>8.10, 6.10, 7.40, 9.50, 8.90, 9.10, 10.10, 10.50, 11.10, 10.10, 10.90,
>>11.30, 13.40, 13.50, 12.80, 11.50, 13.10, 13.50, 11.10, 10.50, 8.50,
>>10.10, 10.70, 13.60, 11.90, 14.90, 10.90, 10.90, 12.80, 12.10, 9.10,
>>8.30, 8.80, 7.40, 8.40, 10.30, 10.00, 7.00, 8.50, 8.40, 8.60, 6.70,
>>7.30, 6.20, 5.90, 5.90, 5.10, 5.80, 5.60, 6.50, 6.60, 11.70, 11.30,
>>8.70, 7.10, 6.90, 4.30, 3.80, 4.30, 3.30, 2.30, 2.30, 3.20, 3.20,
>2.90,
>>2.30, 1.50, 1.80, 2.90, 2.40, 1.80, 2.40, 2.30, 2.60, 1.80, 2.30,
>1.90,
>>2.20, 2.80, 2.40, 1.00, 1.10, 1.60, 2.30, 2.50, 3.30, 3.40, 3.20,
>4.50)
>>
>>
>>Thank you for your attention
>>Stefano
>>
>>
>> (oo)
>>--oOO--( )--OOo----------------
>>Stefano Sofia PhD
>>Civil Protection - Marche Region
>>Meteo Section
>>Snow Section
>>Via del Colle Ameno 5
>>60126 Torrette di Ancona, Ancona
>>Uff: 071 806 7743
>>E-mail: stefano.sofia using regione.marche.it
>>---Oo---------oO----------------
>>
>>________________________________________
>>Da: Jim Lemon [drjimlemon using gmail.com]
>>Inviato: mercoledì 13 maggio 2020 11.01
>>A: Stefano Sofia; r-help mailing list
>>Oggetto: Re: [R] Classification of wind events
>>
>>Hi Stefano,
>>Given only one observation point you will find it difficult. If your
>>automatic weather station is in the low area where the foehn wind is
>>felt, it can only be distinguished from a dry katabatic wind if the
>>upwind conditions are known. There is a similar but milder version of
>>this in eastern Australia, but it is usually of the latter sort. There
>>may be a way to measure turbulence above the peak of the high ground
>>with radar or something, but I'm not familiar with that.
>>
>>Jim
>>
>>On Tue, May 12, 2020 at 6:13 PM Stefano Sofia
>><stefano.sofia using regione.marche.it> wrote:
>>>
>>> Dear R list users,
>>> I am aware that this question is not strictly related, at the
>present
>>moment, to R code and it is more general. Please forgive me, but I
>need
>>to share my thoughts with you.
>>>
>>> Foehn conditions on the southern slope of Alps happen with strong
>>northerly flows that impact perpendicularly over the Apls. This
>>situation triggers strong northerly leeward winds.
>>> Given a single automatic weather station, I would like to identify
>>these periods starting from wind direction and wind intensity data.
>>Frequency of data is quarter of hour.
>>> I would really find difficult to detect the moving windows of these
>>events:
>>> - I can't analyse data day by day;
>>> - at the beginning and at the end of each event, when the process is
>>not at full speed yet, the rotation is not always perfectly
>>identifiable;
>>> - I cannot claim in principle that the direction of each consecutive
>>observation is costantly and strictly from the chosen direction.
>>>
>>> Does anybody have a clue on how to start to build this process in
>the
>>right way?
>>>
>>> Thank you for your attention and your help
>>> Stefano
>>>
>>> (oo)
>>> --oOO--( )--OOo----------------
>>> Stefano Sofia PhD
>>> Civil Protection - Marche Region
>>> Meteo Section
>>> Snow Section
>>> Via del Colle Ameno 5
>>> 60126 Torrette di Ancona, Ancona
>>> Uff: 071 806 7743
>>> E-mail: stefano.sofia using regione.marche.it
>>> ---Oo---------oO----------------
>>>
>>> ________________________________
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