Change line color depending on y value with ggplot2

Question

I have a question about line colors in ggplot2. I need to compile solar radiation data, but I only have 6 hourly data, so geom_line do not give a “good” way out. I tried geom_smooth and the result is close to what I need. But I have a new question: is it possible to change the color of the line depending on the value of y?

The code used for the chart,

 library(ggplot2) library(lubridate) # Lectura de datos datos.uvi=read.csv("serie-temporal-1.dat",sep=",",header=T,na.strings="-99.9") datos.uvi=within(datos.uvi, fecha <- ymd_h(datos.uvi$fecha.hora)) # geom_smooth ggplot(data=datos.uvi, aes(x=fecha, y=Rad_Global_.mW.m2., colour="GLOBAL")) + geom_smooth(se=FALSE, span=0.3) 

In the desired output, the line should be red for radiation values ​​up to 250, green in the range 250-500 and blue for values ​​above 500.

Is this possible with geom_smooth ? I tried to reuse the code here , but could not find the point.

Data used for the chart:

 dput(datos.uvi) structure(list(fecha.hora = c(2016012706L, 2016012712L, 2016012718L, 2016012800L, 2016012806L, 2016012812L, 2016012818L, 2016012900L, 2016012906L, 2016012912L, 2016012908L, 2016013000L), latitud = c(37.75, 37.75, 37.75, 37.75, 37.75, 37.75, 37.75, 37.75, 37.75, 37.75, 37.75, 37.75), longitud = c(-1.25, -1.25, -1.25, -1.25, -1.25, -1.25, -1.25, -1.25, -1.25, -1.25, -1.25, -1.25), altitud = c(300L, 300L, 300L, 300L, 300L, 300L, 300L, 300L, 300L, 300L, 300L, 300L ), cobertura_nubosa = c(0.91, 0.02, 0.62, 1, 0.53, 0.49, 0.01, 0, 0, 0.13, 0.62, 0.84), longitud_de_onda_inicial.nm. = c(284.55, 284.55, 284.55, 284.55, 284.55, 284.55, 284.55, 284.55, 284.55, 284.55, 284.55, 284.55), Rad_Global_.mW.m2. = c(5e-04, 259.2588, 5, 100.5, 1, 886.5742, 110, 40, 20, 331.3857, 0, 0), Rad_Directa_.mW.m2. = c(0, 16.58034, 0, 0, 0, 202.5683, 0, 0, 0, 89.81712, 0, 0), Rad_Difusa_.mW.m2. = c(0, 242.6785, 0, 0, 0, 684.0059, 0, 0, 0, 241.5686, 0, 0), Angulo_zenital_.º. = c(180, 56.681, 180, 180, 180, 56.431, 180, 180, 180, 56.176, 180, 180 ), blank = c(NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA), fecha = structure(c(1453874400, 1453896000, 1453917600, 1453939200, 1453960800, 1453982400, 1454004000, 1454025600, 1454047200, 1454068800, 1454054400, 1454112000), tzone = "UTC", class = c("POSIXct", "POSIXt"))), row.names = c(NA, -12L), .Names = c("fecha.hora", "latitud", "longitud", "altitud", "cobertura_nubosa", "longitud_de_onda_inicial.nm.", "Rad_Global_.mW.m2.", "Rad_Directa_.mW.m2.", "Rad_Difusa_.mW.m2.", "Angulo_zenital_.º.", "blank", "fecha"), class = "data.frame") 

Thanks in advance.

Answer 1

Calculate anti-aliasing outside of ggplot2, and then use geom_segment :

 fit <- loess(Rad_Global_.mW.m2. ~ as.numeric(fecha), data = datos.uvi, span = 0.3) #note the warnings new.x <- seq(from = min(datos.uvi$fecha), to = max(datos.uvi$fecha), by = "5 min") new.y <- predict(fit, newdata = data.frame(fecha = as.numeric(new.x))) DF <- data.frame(x1 = head(new.x, -1), x2 = tail(new.x, -1) , y1 = head(new.y, -1), y2 = tail(new.y, -1)) DF$col <- cut(DF$y1, c(-Inf, 250, 500, Inf)) ggplot(data=DF, aes(x=x1, y=y1, xend = x2, yend = y2, colour=col)) + geom_segment(size = 2) 

Notice what happens at the cut points. If it can be more visually appealing, to make the x-prediction grid very thin, then use geom_point . However, the schedule will be slow.

Answer 2

This is not what you asked for, but it can serve the same purpose: instead of coloring the line, color the background. First we create a dataframe of rectangular / limit coordinates.

 rect_data <- data.frame(xmin=min(datos.uvi$fecha), xmax=max(datos.uvi$fecha), ymin=c(0,250,500), ymax=c(250,500,max(datos.uvi$Rad_Global_.mW.m2.)), col=c("red","green","blue")) 

Then add them to the chart using scale_fill_identity ()

 ggplot(data=datos.uvi) + geom_smooth(aes(x=fecha, y=Rad_Global_.mW.m2.),colour="black",se=FALSE, span=0.3) + geom_rect(data=rect_data, aes(xmin=xmin,xmax=xmax,ymin=ymin,ymax=ymax,fill=col),alpha=0.1)+ scale_fill_identity()