如何使 r 中图表上的一系列点具有不同的颜色

Question

I have made a graph with the year on the x-axis and sea level rise on the y-axis. I am trying to make the data from 2025 (predictions) a different colour to that before 2025. I have grouped and labeled the predicted data using this code and have also included the code for my graph

predictions=data[which(data$Year>2024 & data$Year<2121),] plot(data$Sea.Level..cm.~data$Year,xlab="Year",ylab="Sea Level (cm)",pch=21,col=c("Blue"))

How do I go from here in making the predictions red but the previous data blue? Thanks in advance

Answer 1

You can try something like this. Toy data used.

vec <- c( rep(2001,10), rep(2002, 3) )

tf <- (vec < 2002) + 1

barplot( 1:length(vec), vec, col=c("red","blue")[tf], names=vec )

Answer 2

You can provide a vector of colours to plot in the col argument. eg following your existing syntax:

predictions <- rep("red", nrow(data))
predictions[which(data$Year>2024 & data$Year<2121)] <- "blue"
plot(data$Sea.Level..cm.~data$Year,xlab="Year",ylab="Sea Level (cm)",pch=21,col=predictions)