# Legends and Dates in R plots

Posted: December 5th, 2011 | Author: | Filed under: Uncategorized | 2 Comments »

After looking up how to create a legend using ?legend and searching the R forums for the 86586586th time, I’ve decided to write my own post with a few examples and tricks I’ve picked up. I also provide example code for using dates as an x-axis.

I do most of my heavy computation in Python, leaving R for primarily making pretty plots, exploratory data analysis (EDA) when I first get my hands on a data set, and using my favorite R packages/functions that I’ll never implement on my own (ie Random Forests, CART, SVM). Below is an example plot, with two sets of numbers, a legend, and dates on the axis. Hopefully this is more helpful than the R documentation. # pick a length, and generate two random normals of this length
len = 43
vals = rnorm(len,0,1)
vals2 = rnorm(len,0,.5)

# pick an initial date in form YYYYMMDD, then generate a years worth of weekly dates
date = 20110201
mydates<-as.Date(as.character(date),"%Y%m%d") for(i in 1:52){ # mydates = c(mydates,mydates[length(mydates)]+7) } # rename something shorter x=mydates[2:(len+1)] # set graphical parameters and plot both random normals, use xaxt="n" to eliminate the x-axis par(mfrow=c(1,1)) plot(vals,type="l",col="blue",xaxt="n",ylab="y axis label",xlab="",main="Plot Title") lines(vals2,col="red") # add back an x-axis with dates, las and cex.axis set direction and size of dates axis(1, at=1:len,x,las=2,cex.axis=.9) # add a legend, lwd sets line width, you can use x,y coordinates instead of "bottomleft" legend("bottomleft", c("thing1","thing2"), col = c("blue", "red"), lwd = 1, title="legend title")

### 2 Comments on “Legends and Dates in R plots”

1. 1 Clare said at 4:37 pm on January 15th, 2014:

This is the first legend advice that clearly tells you how to put the lines in. Thanks

2. 2 umesh said at 1:44 am on January 10th, 2015:

This has helped me to plot the scatterplot with proper legend. Thanks