Mixing line chart and dots points in baseline of chart in R

Question

I have built a chart in R with two series, but I want to add a coloured bar at the bottom of the chart:

The data to be plotted is

2013-01-01 12:35:00      0
2013-01-01 12:45:00      1
2013-01-01 13:00:00      1
....
2013-01-01 13:00:00      2

where 0 is green, 1 is orange and 2 is red. Datetime is aligned with data X in original chart.

This is the code for the chart (without coloured bar):

datos_tem <- dbGetQuery(connection, paste("SELECT temp_int,hum_int,datetime FROM datalog_v2 WHERE host_id=41 and datetime>='2014-02-01 00:00:00' and datetime<='2014-02-01 23:59:00';", sep=""))
dbDisconnect(connection)

datos_tem$datetime <- as.POSIXct(datos_tem$datetime)
datos_tem$temp_int <- as.numeric(datos_tem$temp_int)
datos_tem$hum_int <- as.numeric(datos_tem$hum_int)


#gg <- qplot(datos_tem$datetime, datos_tem$temp_int) + geom_line()        # first line
#gg <- gg + geom_line(aes( x=datos_tem$datetime, y=datos_tem$hum_int )) # add the second line!

png(file.path("/tmp/", paste("comp",".png",sep="_")))
Molten <- melt(datos_tem, id.vars = "datetime")
ggplot(Molten, aes(x = datetime, y = value, colour = variable)) + geom_line() +
  scale_y_continuous(limits=c(0, 100)) +
   xlab("Tiempo") +
   ylab("Temperatura --- (ºC) y Humedad (%)")+ 
  geom_line(size=1.9)+
 scale_color_manual(values=c("#FF0000", "#0000FF"), 
                       name="Medidas",
                       labels=c("Temperature", "Humidity"))

So, I want to add something like my example to my code. Is it possible?

Data for lines are:

      temp_int  hum_int            datetime
      11.6      76.8     2014-02-01 00:00:00
      11.4      77.8     2014-02-01 00:15:00
      11.3      79.4     2014-02-01 00:30:00
      .....

And data for the bar at bottom is:

datetime                DPV
2013-01-01 12:35:00      0
2013-01-01 12:45:00      1
2013-01-01 13:00:00      1
....
2013-01-01 13:00:00      2

Better!! I've changed my data and now I have:

datetime,temp_int,hum_int,dpv
"2014-02-15 00:00:00",67.2,13.6,"red"
"2014-02-15 00:15:00",63.4,13.8,"yellow"
"2014-02-15 00:30:00",61.2,14.2,"green"
"2014-02-15 00:45:00",60.4,14.5,"green"
....

Answer 1

It hard to answer without actual data but here some ideas to start with.

Made some sample data consisting of x values, temp values for lines and id values used to color bar.

set.seed(1)
df<-data.frame(x=1:100,temp=runif(100,10,50),id=sample(1:3,100,replace=TRUE))

One solution is to use geom_tile() and set y values to 0 and use id for the fill=. Problem with this solution is that height of bar will depend on range of your data. You can increase the height by calling several geom_tile() calls with different y values.

ggplot(df,aes(x))+geom_line(aes(y=temp))+
  geom_tile(aes(y=0,fill=factor(id)))

Another possibility is to use geom_bar() with stat="identity" and set y value height of bars you need. With argument width= you can change width of bars to ensure that there is no space between bars.

ggplot(df,aes(x))+geom_line(aes(y=temp))+
  geom_bar(aes(y=4,fill=factor(id)),stat="identity",width=1)

UPDATE - solution with OP data

Data provided in question.

df<-read.table(text="datetime,temp_int,hum_int,dpv
        2014-02-15 00:00:00,67.2,13.6,red
        2014-02-15 00:15:00,63.4,13.8,yellow
        2014-02-15 00:30:00,61.2,14.2,green
        2014-02-15 00:45:00,60.4,14.5,green",header=T,sep=",")

Converting datetime column to POSIXct.

df$datetime <- as.POSIXct(df$datetime)

Melting data frame to long format.

library(reshape2)
df.melt<-melt(df,id.vars=c("datetime","dpv"))

Now for plotting use melted data frame. Argument colour= should be placed inside the aes() of geom_line() because color change border of bars if placed inside the ggplot() call. For geom_bar() use dpv as fill= and also use scale_fill_identity() because dpv contains actual color names. If you need to have bars that are close to each other use width=900. I set 900 because you have time interval of 15 minutes that correspond to 900 seconds (1 second is unit in this case).

ggplot(df.melt, aes(x = datetime, y = value)) + 
  geom_line(aes(colour = variable),size=1.9) +
  geom_bar(aes(y=4,fill=dpv),stat="identity",width=900)+
  scale_fill_identity()