#    INTERACTIONS IN R (ANOVA)SCRIPT FILE.
#    www_statstutor_ac_uk Community Project.
#    Sofia Maria Karadimitriou and Ellen Marshall, Sheffield University.
#     Reviewed by Jim Bull, University of Swansea.

#    Dataset: diet csv.
#    Resource: Interactions in ANOVA in R.

#Open the diet dataset which is saved as a csv file and call it dietR.  
#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.
dietR<-read.csv("D:\\diet.csv",header=T,sep=",")
#Tell R we are using the diet dataset until further notice using attach.
#This means that 'Height' can be used instead of dietR$Height.
attach(dietR) 

#R assumes all numeric values are continuous so tell it that ‘gender’ and 'Diet' are factors.
#as.factor(variable) is a quick way of defining factors or use the factor command to give categories names. 
Diet<-as.factor(Diet)
# The factor command uses variable<-factor(variable,c(category numbers),labels=c(category names)).
gender<-factor(gender,c(0,1),labels=c('Female','Male'))

#To generate an interaction plot for weight lost and the interaction of diet and gender 
#use the interaction.plot(independent1,independent2,dependent) command
interaction.plot(Diet, gender, weightlost,main="Mean weight lost by diet and gender",ylab = "mean of weightlost",xlab = "Type of Diet")

## Changing the type of lines ##.
#lty specifies the type of lines
#lwd specifies the thickness of the lines. If you want the lines to be different, try lwd=c(1,3)
#col specifies the colours of the lines.
interaction.plot(Diet, gender, weightlost,lty = c(1, 12),col=c(2:3),lwd = 3,ylab = "mean of weightlost",
xlab = "Type of Diet",main="Mean weight lost by diet and gender")

## Adding and editing points ##.
#Type = b adds points to the line.
#pch controls the shape of the points.
interaction.plot(Diet, gender, weightlost, main="Mean weight lost by diet and gender", type="b",pch=c(18,24),lty = c(1, 12),col=c(2:3),lwd = 3,ylab = "mean of weightlost",
xlab = "Type of Diet",main="Mean weight lost by diet and gender")

## Legend formatting ##.
#trace.label controls the name of the legend eg Gender.
#leg.bty ="o" puts a box around the legend.
#leg.bg=" " controls the background colour of the legend.
#Use ?interaction.plot to find out more.

interaction.plot(Diet, gender, weightlost, main="Mean weight lost by diet and gender",type="b",pch=c(18,24),lty = c(1, 12),col=c(2:3),lwd = 3,trace.label = "Gender",leg.bty="o", leg.bg="beige",ylab = "mean of weightlost",
xlab = "Type of Diet")