#    SCATTERPLOTS IN R SCRIPT FILE.
#    www_statstutor_ac_uk Community Project.
#    Sofia Maria Karadimitriou and Ellen Marshall, Sheffield University.
#    Reviewed by Jim Bull, University of Swansea.
#    Dataset: Birthweight reduced csv.
#    Resource: Scatterplots in R.

#Open the birthweight reduced dataset which is saved as a csv file and call it birthweightR.  
#If your file is saved as a standard Excel file, save it as a csv file first.  
#You will need to change the command depending on where you have saved the file.
birthweightR<-read.csv("D:\\Birthweight reduced.csv",header=T,sep=",")

#Tell R we are using the birthweight dataset until further notice using attach.
#This means that 'Gestation' can be used instead of birthweightR$Gestation.
attach(birthweightR) 

#R assumes all numeric values are continuous so tell it that ‘smoker’ is a factor. 
#and attach labels to the categories (for example 0 in smoker means the mother is a non-smoker).
# The factor command uses variable<-factor(variable,c(category numbers),labels=c(category names)).
smoker<-factor(smoker,c(0,1),labels=c('Non-smoker','Smoker'))

#Plotting the relationship between two continuous variables.
plot(Gestation,Birthweight,main='Scatterplot of gestational age and birthweight')
#main='' gives the title.
#xlab'' controls the x axis label.
#ylab'' controls the y axis label.
#pch changes the shape of the scatter, pch=4 gives crosses.
#cex changes the size of the scatter.
#lwd changes the width of the outline.

plot(Gestation,Birthweight,main='Scatterplot of gestational age and birthweight',xlab='Gestation (weeks)',ylab='Birthweight (lbs)',pch=4,cex=1.5,lwd=3)


#Creating a plot with different colours by Group.
plot(Gestation,Birthweight,col=c('red','blue')[smoker],main='Scatterplot by smoker', pch=c(1,4)[smoker],xlab='Gestation (weeks)',ylab='Birthweight(lbs)')

#adding a legend with the labels for each group.
legend(x="topleft", legend = levels(smoker), col=c('red','blue'), pch=c(1,4))

#Producing a scatterplot matrix.
pairs(~Birthweight+Gestation+motherage,main='Birth weight scatterplot matrix',col=c('red','blue')[smoker],pch=c(1,4)[smoker])

#Adding a regression line to the plot.
plot(Gestation,Birthweight,main='Scatterplot of gestational age and birthweight',xlab='Gestation (weeks)',ylab='Birthweight(lbs)')
abline(lm(Birthweight~Gestation),col='red',lwd=2)