### Passiflora flower size r code

PV<-read.csv("Passiflora_visits.csv",header=TRUE)
#head(PV)
mean(PV$Total_visitors); var(PV$Total_visitors)

modellm<-lm(PV$Total_visitors ~ PV$Flower_diam_mm)
summary(modellm)

modelP<-glm(PV$Total_visitors ~ PV$Flower_diam_mm,family="poisson")

modelQP<-glm(PV$Total_visitors ~ PV$Flower_diam_mm,family="quasipoisson")
summary(modelQP)



plot(PV,pch=16,col="red")
abline(modelQP,col="red",lwd=2)
abline(modelP,col="blue",lwd=2,lty=3)
abline(modellm,col="black",lwd=2)

## for modelQP
intercept<-modelQP$coeff[1]
slope<-modelQP$coeff[2]
mid_x_value<-range(PV$Flower_diam_mm)[1]+0.5*diff(range(PV$Flower_diam_mm)) # get the middle of the x range
y<-slope*mid_x_value+intercept + 0.35 # 0.35 is a small offset to position text above line
text(mid_x_value,y,"Poisson and quasipoisson fit", srt=3,col="blue") # 3 degrees is a first guestimate for the angle




###### Calculating precise angle in degrees taking into account the x and y limits of
###### the plot and the dimensions of the plot window
###### complicated but necessary as the printing text at an angle argument srt=
###### requires degrees 


plot(PV,pch=16,col="red")
abline(modelQP,col="red",lwd=2)
abline(modelP,col="blue",lwd=2,lty=3)
abline(modellm,col="black",lwd=2)

plotwindow_adjust<-par("pin")[2]/par("pin")[1]
mylims <- par("usr")
mid_x_value<-range(PV$Flower_diam_mm)[1]+0.5*diff(range(PV$Flower_diam_mm))

#### Poisson and quasipoisson model
intercept<-modelQP$coeff[1]
slope<-modelQP$coeff[2]

### y=slope*x+ intercept

y<-slope*mid_x_value+intercept + 0.35 # 0.35 is a small offset to position text above line

left<-slope*mylims[1]+intercept
right<-slope*mylims[2]+intercept
height<-right-left
spread<-mylims[4]-mylims[3]
tangent<-height/spread
plotwindow_adjust<-par("pin")[2]/par("pin")[1]
rotation_in_degrees<-plotwindow_adjust*atan(tangent) * 180 / pi
text(mid_x_value,y,"Poisson and quasipoisson fit", srt=rotation_in_degrees,col="blue")


###Linear model
intercept<-modellm$coeff[1]
slope<-modellm$coeff[2]
y<-slope*mid_x_value+intercept + 0.35 


left<-slope*mylims[1]+intercept
right<-slope*mylims[2]+intercept
height<-right-left
spread<-mylims[4]-mylims[3]
tangent<-height/spread
rotation_in_degrees<-plotwindow_adjust*atan(tangent) * 180 / pi

text(mid_x_value,y,"Linear model fit", srt=rotation_in_degrees,col="blue")