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I've got sensor data that looks like this: 

tm <- seq(1,17)
chg <-    c(13.6,13.7,13.8,13.9,14.1,14.2,14.4,14.6,14.7,14.9,14.9,15.0,15.0,13.7,13.7,13.6,13.7)
batt_A <- c(   1,   1,   1,   1,   1,   1,   1,   1,   1,   2,   2,   2,   2,   3,   3,   0,   0)
batt_B <- c(   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   1,   1)
bus    <- c(12.4,12.5,12.4,11.7,11.6,12.2,12.4,11.8,11.7,11.5,12.1,12.0,11.6,11.5,11.4,12.6,12.5)
pwr <- data.frame(tm,batt_A,batt_B,chg,bus)

I want to create two line graphs (chg and bus against tm) in separate facet panels. The twist is that I want also to have each line colored to represent which battery it's tracking. So if batt_A>0, it's charging and I want the charge line to be green; and if batt_A==0, it's on the bus, and I want the bus line to be green. Same for batt_B, except the lines would be blue (or whatever color).

I get the melt + facet combination, but how to add the coloring?

(ps: I'm using facets because there are 6 more sensors varying on the same timescale and I want to watch them all)

With Andrie's answer below, I got to this solution, but the recode is horrible: 

mpwr <- melt(pwr, id.vars=1:3)

mpwr$batt <- ''
mpwr$batt <- ifelse(mpwr$batt_A>0 & mpwr$variable=="chg", "A", mpwr$batt)
mpwr$batt <- ifelse(mpwr$batt_B>0 & mpwr$variable=="chg", "B", mpwr$batt)
mpwr$batt <- ifelse(mpwr$batt_A==0 & mpwr$variable=="bus", "A", mpwr$batt)
mpwr$batt <- ifelse(mpwr$batt_B==0 & mpwr$variable=="bus", "B", mpwr$batt)
mpwr$batt <- as.factor(mpwr$batt)

ggplot(mpwr, aes(x=tm, group=1)) + 
   geom_line(aes(y=value, colour=batt)) +
   geom_line(aes(y=value, colour=batt)) +
   facet_grid(~variable) +
   scale_colour_discrete("Charging")

The data processing could be cleaned up, but I think I'm there!

mnel
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wylbur
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1 Answers1

4

Something like the following:

library(reshape2)
library(ggplot2)

mpwr <- melt(pwr, id.vars=1:3)

ggplot(mpwr, aes(x=tm, group=1)) + 
  geom_line(aes(y=value, colour=factor(batt_A!=0))) +
  geom_line(aes(y=value, colour=factor(batt_B!=0))) +
  facet_grid(~variable) +
  scale_colour_discrete("Charging")

enter image description here

Andrie
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  • very close, Andrie! The lines should have opposite colors, though. So if chg is right, the colors for bus should be flipped showing that the red battery is on bus while the blue battery is charging. I'll play with it, and much appreciated. – wylbur Aug 14 '12 at 21:37