Stefano Sofia
2015-Sep-11 09:46 UTC
[R] how to divide a data frame of half-hourly wind observations into subset of three hours
Dear R-users, from a data frame of half-hourly wind observations (direction and speed, three years data), I need to evaluate the first main direction for each period of three hours (h03, h06, h09, h12, h15, h18, h21, h24 of each day). The command "windRose" of the package "openair" crates a data frame that contains the information I need. Can I ask you which is the most efficient way to run the windRose command for each subset of three hours? The initial data frame is called wind_df is like Date Direction Speed 2015-06-30 00:30:00 315 2.9 2015-06-30 01:00:00 338 3.5 2015-06-30 01:30:00 23 4.8 2015-06-30 02:00:00 338 4.1 2015-06-30 02:30:00 135 1.1 2015-06-30 03:00:00 45 2.7 2015-06-30 03:30:00 1.7 2015-06-30 04:00:00 293 1 2015-06-30 04:30:00 45 1.5 2015-06-30 05:00:00 45 2.3 ... The command for the wind rose creation is output1_df <- windRose(wind_df, ws="Speed", wd="Direction", layout=c(1,1), ws.int=4, angle=22.5, type="default", bias.corr=TRUE, cols="default", grid.line=NULL, width=2, seg=NULL, auto.text=TRUE, breaks=c(0,0.3,1.5,3.4,5.4,7.9,10.7,13.8,17.1,20.7,24.4,28.4,32.6,40), offset=5, normalise=TRUE, max.freq=NULL, paddle=TRUE, key.header=NULL, key.footer="(km/hr)", key.position="bottom", key=TRUE, dig.lab=2, statistic="prop.count", pollutant=NULL, annotate=TRUE, border=NA, par.settings=list(fontsize=list(text=10))) and I evaluate the first main direction through output2_df <- output1_df$data output2_df$wd[output2_df$freqs == max(output2_df$freqs)]) Thank you for your attention and your help Stefano Sofia ________________________________ AVVISO IMPORTANTE: Questo messaggio di posta elettronica pu? contenere informazioni confidenziali, pertanto ? destinato solo a persone autorizzate alla ricezione. I messaggi di posta elettronica per i client di Regione Marche possono contenere informazioni confidenziali e con privilegi legali. Se non si ? il destinatario specificato, non leggere, copiare, inoltrare o archiviare questo messaggio. Se si ? ricevuto questo messaggio per errore, inoltrarlo al mittente ed eliminarlo completamente dal sistema del proprio computer. Ai sensi dell?art. 6 della DGR n. 1394/2008 si segnala che, in caso di necessit? ed urgenza, la risposta al presente messaggio di posta elettronica pu? essere visionata da persone estranee al destinatario. IMPORTANT NOTICE: This e-mail message is intended to be received only by persons entitled to receive the confidential information it may contain. E-mail messages to clients of Regione Marche may contain information that is confidential and legally privileged. Please do not read, copy, forward, or store this message unless you are an intended recipient of it. If you have received this message in error, please forward it to the sender and delete it completely from your computer system. [[alternative HTML version deleted]]
PIKAL Petr
2015-Sep-11 11:05 UTC
[R] how to divide a data frame of half-hourly wind observations into subset of three hours
Hi if you have full set of data, so no observation is missing, you can split your data frame values e.g. by split(yourdata, trunc(0:nrow(yourdata))/6) and use lapply or for cycle. If you need to cut according to dates you can use ?cut POSIX date. Cheers Petr> -----Original Message----- > From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Stefano > Sofia > Sent: Friday, September 11, 2015 11:47 AM > To: r-help at r-project.org > Subject: [R] how to divide a data frame of half-hourly wind > observations into subset of three hours > > Dear R-users, > from a data frame of half-hourly wind observations (direction and > speed, three years data), I need to evaluate the first main direction > for each period of three hours (h03, h06, h09, h12, h15, h18, h21, h24 > of each day). > > The command "windRose" of the package "openair" crates a data frame > that contains the information I need. > Can I ask you which is the most efficient way to run the windRose > command for each subset of three hours? > > The initial data frame is called wind_df is like > > Date Direction Speed > 2015-06-30 00:30:00 315 2.9 > 2015-06-30 01:00:00 338 3.5 > 2015-06-30 01:30:00 23 4.8 > 2015-06-30 02:00:00 338 4.1 > 2015-06-30 02:30:00 135 1.1 > 2015-06-30 03:00:00 45 2.7 > 2015-06-30 03:30:00 1.7 > 2015-06-30 04:00:00 293 1 > 2015-06-30 04:30:00 45 1.5 > 2015-06-30 05:00:00 45 2.3 > ... > > The command for the wind rose creation is > output1_df <- windRose(wind_df, ws="Speed", wd="Direction", > layout=c(1,1), ws.int=4, angle=22.5, type="default", bias.corr=TRUE, > cols="default", grid.line=NULL, width=2, seg=NULL, auto.text=TRUE, > breaks=c(0,0.3,1.5,3.4,5.4,7.9,10.7,13.8,17.1,20.7,24.4,28.4,32.6,40), > offset=5, normalise=TRUE, max.freq=NULL, paddle=TRUE, key.header=NULL, > key.footer="(km/hr)", key.position="bottom", key=TRUE, dig.lab=2, > statistic="prop.count", pollutant=NULL, annotate=TRUE, border=NA, > par.settings=list(fontsize=list(text=10))) > > and I evaluate the first main direction through > output2_df <- output1_df$data > output2_df$wd[output2_df$freqs == max(output2_df$freqs)]) > > > Thank you for your attention and your help > Stefano Sofia > > > ________________________________ > > AVVISO IMPORTANTE: Questo messaggio di posta elettronica pu? contenere > informazioni confidenziali, pertanto ? destinato solo a persone > autorizzate alla ricezione. I messaggi di posta elettronica per i > client di Regione Marche possono contenere informazioni confidenziali e > con privilegi legali. Se non si ? il destinatario specificato, non > leggere, copiare, inoltrare o archiviare questo messaggio. Se si ? > ricevuto questo messaggio per errore, inoltrarlo al mittente ed > eliminarlo completamente dal sistema del proprio computer. Ai sensi > dell?art. 6 della DGR n. 1394/2008 si segnala che, in caso di necessit? > ed urgenza, la risposta al presente messaggio di posta elettronica pu? > essere visionata da persone estranee al destinatario. > IMPORTANT NOTICE: This e-mail message is intended to be received only > by persons entitled to receive the confidential information it may > contain. E-mail messages to clients of Regione Marche may contain > information that is confidential and legally privileged. Please do not > read, copy, forward, or store this message unless you are an intended > recipient of it. 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