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Asked: 2026-05-26T01:14:42+00:00

I am trying to plot hourly meteorological data coming from a meteorological station with

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I am trying to plot hourly meteorological data coming from a meteorological station with ggplot2 (it’s my first time with ggplot). I’ve managed to plot daily data but having some problem when downscaling to hourly data. Data files look like that:

FECHA H_SOLAR;DIR_M;VEL_M;TEMP_M;HR;PRECIP
01/06/14 00:50:00;314.3;1.9;14.1;68.0;-99.9
01/06/14 01:50:00;322.0;1.6;13.3;68.9;-99.9
01/06/14 02:50:00;303.5;2.1;12.3;70.9;-99.9
01/06/14 03:50:00;302.4;1.6;11.6;73.1;-99.9
01/06/14 04:50:00;306.5;1.2;10.9;76.4;-99.9
01/06/14 05:50:00;317.1;0.8;12.6;71.5;-99.9
01/06/14 06:50:00;341.8;0.0;17.1;58.8;-99.9
01/06/14 07:50:00;264.6;1.2;21.8;44.9;-99.9
01/06/14 08:50:00;253.8;2.9;24.7;32.2;-99.9
01/06/14 09:50:00;254.6;3.7;26.7;27.7;-99.9
01/06/14 10:50:00;250.7;4.3;28.3;24.9;-99.9
01/06/14 11:50:00;248.5;5.3;29.1;22.6;-99.9
01/06/14 12:50:00;242.8;4.7;30.3;20.4;-99.9
01/06/14 13:50:00;260.7;4.9;31.3;17.4;-99.9
01/06/14 14:50:00;251.8;5.1;31.9;17.1;-99.9
01/06/14 15:50:00;258.1;4.6;32.4;15.3;-99.9
01/06/14 16:50:00;254.3;5.7;32.4;14.0;-99.9
01/06/14 17:50:00;252.5;4.6;32.0;14.1;-99.9
01/06/14 18:50:00;257.4;3.8;31.1;14.9;-99.9
01/06/14 19:50:00;135.8;4.2;26.0;41.2;-99.9
01/06/14 20:50:00;126.0;1.7;23.5;48.7;-99.9
01/06/14 21:50:00;302.8;0.7;21.6;53.9;-99.9
01/06/14 22:50:00;294.2;1.1;19.3;67.4;-99.9
01/06/14 23:50:00;308.5;1.0;17.5;72.4;-99.9

I have used this R commands to plot the data:

datos=read.csv("utiel.dat",sep=";",header=T,na.strings="-99.9")

dia=as.Date(datos[,1],"%y/%m/%d")       # Crear índice dia
veloc=zoo(datos[,c("VEL_M")],dia)       

gveloc=ggplot(data=datos,aes(dia,veloc))

gveloc + geom_point(colour="blue",cex=1) + ylab("Velocidad (km/h)") + xlab("Fecha") + opts(title="Velocidad media horaria") + scale_x_date(limits = as.Date(c("2007-01-01","2007-01-31")),format = "%Y-%m-%d")

and got this monthly graph with all data from a single day in the same x coordinate (i.e. the same day as it could be expected)

Hourly wind data with ggplot2

How can I manage to read not only the day but the time so each point can be plotted in it’s own x/time coordinate? I think the problem starts before plotting but I couldn’t find how to read date as YY/MM/DD H:M:S

Thanks in advance

Solution: Just an addition to put the code has worked for me

 datos$dia=as.POSIXct(datos[,1], format="%y/%m/%d %H:%M:%S")  # Read date/time as POSIXct

 ggplot(data=datos,aes(x=dia, y=TEMP_M)) + 
   geom_point(colour="red") + 
   ylab("Temperatura (ºC)") + 
   xlab("Fecha") + 
   opts(title="Temperatura media") + 
   scale_x_datetime(limits=c(as.POSIXct('2008/02/01'), as.POSIXct('2008/02/02')) ,format =  "%Y-%m-%d")

Hope it helps someone else, thanks Andrie and G.Grothendieck

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1 Answer

  1. Editorial Team

    as.Date only capture the date element. To capture time, you need to use as.POSIXct:

    Recreate your data:

    zz <- tempfile()
cat("
FECHA H_SOLAR;DIR_M;VEL_M;TEMP_M;HR;PRECIP
01/06/14 00:50:00;314.3;1.9;14.1;68.0;-99.9
01/06/14 01:50:00;322.0;1.6;13.3;68.9;-99.9
01/06/14 02:50:00;303.5;2.1;12.3;70.9;-99.9
01/06/14 03:50:00;302.4;1.6;11.6;73.1;-99.9
01/06/14 04:50:00;306.5;1.2;10.9;76.4;-99.9
01/06/14 05:50:00;317.1;0.8;12.6;71.5;-99.9
01/06/14 06:50:00;341.8;0.0;17.1;58.8;-99.9
01/06/14 07:50:00;264.6;1.2;21.8;44.9;-99.9
01/06/14 08:50:00;253.8;2.9;24.7;32.2;-99.9
01/06/14 09:50:00;254.6;3.7;26.7;27.7;-99.9
01/06/14 10:50:00;250.7;4.3;28.3;24.9;-99.9
01/06/14 11:50:00;248.5;5.3;29.1;22.6;-99.9
01/06/14 12:50:00;242.8;4.7;30.3;20.4;-99.9
01/06/14 13:50:00;260.7;4.9;31.3;17.4;-99.9
01/06/14 14:50:00;251.8;5.1;31.9;17.1;-99.9
01/06/14 15:50:00;258.1;4.6;32.4;15.3;-99.9
01/06/14 16:50:00;254.3;5.7;32.4;14.0;-99.9
01/06/14 17:50:00;252.5;4.6;32.0;14.1;-99.9
01/06/14 18:50:00;257.4;3.8;31.1;14.9;-99.9
01/06/14 19:50:00;135.8;4.2;26.0;41.2;-99.9
01/06/14 20:50:00;126.0;1.7;23.5;48.7;-99.9
01/06/14 21:50:00;302.8;0.7;21.6;53.9;-99.9
01/06/14 22:50:00;294.2;1.1;19.3;67.4;-99.9
01/06/14 23:50:00;308.5;1.0;17.5;72.4;-99.9
", file=zz)

datos=read.csv(zz, sep=";", header=TRUE, na.strings="-99.9")

    Convert dates to POSIXct and print:

    library(ggplot2)

datos=read.csv(zz, sep=";", header=TRUE, na.strings="-99.9")

datos$dia=as.POSIXct(datos[,1], format="%y/%m/%d %H:%M:%S")  

ggplot(data=datos,aes(x=dia, y=TEMP_M)) + 
  geom_path(colour="red") + 
  ylab("Temperatura (ºC)") + 
  xlab("Fecha") + 
  opts(title="Temperatura media")

    enter image description here

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