# Code initially written by Ryan Sieberg. # First set up a PNG graphics device in which we will print the image. png("../figures/hurshR.png") # Read data from CSV. hursh <- read.csv("../data/hursh.csv") # hursh contains two named columns, 'diameter' and 'velocity'. # The 'par' commands change graphical parameters. cex stands for # "character expansion" and determines the size of text, in this # case, cex.lab changes the size of the label. par(cex.lab=2) # cex.axis changes the size of the axis font. par(cex.axis=1.75) # mar changes the margins of the graph area. par(mar=(c(5,4.7,4,2)+.1)) # Create a linear model for the hursh data. lmhursh<-lm(hursh$velocity ~ hursh$diameter) # Plot the data. plot(hursh$diameter, hursh$velocity, main="", axes=FALSE, xlab="Diameter (microns)", ylab=" Velocity (m/s)", xlim=c(0,20), ylim=c(0,120)) axis(1,pos=0) axis(2,pos=0) # Add a line. The linear model object "lmhursh" contains a list # called "coef", which contains the coefficients of the model. The # first entry is the intercept, and the second is the coefficient for # velocity. They are stored as strings, so we convert them to # numerics before using them in abline. intercept <- as.numeric(lmhursh$coef[1]) slope <- as.numeric(lmhursh$coef[2]) abline(intercept, slope, untf = "FALSE") # With our figue complete, close the connection to the PNG. dev.off()