Make condition for graph generation when there are two points

[JojoSouza]

Could you help me make a condition for the code below. Before explaining what I want, I'll explain in general the purpose of the code. The code basically generates a graph with a few dots and a "prediction" line, so to speak.

If I generate the graph for CDE, notice that it is 4 points, and for ABC it is 2 points. However, I would like to make a condition that when I have two points, the "prediction" line is the mean and I don't use the model function there that I do. So for the ABC graph the line should go towards 6.4.

Could you help me adjust this?

library(dplyr)
library(tidyverse)
library(lubridate)


dmda<-"2021-07-07"

datas <- structure(
  list(Code = c("CDE","CDE","CDE","CDE","ABC","ABC"),
       Days = c(39,40, 41,42,43,44),
       Numbers = c(5.5,5.5,6,6.5,7,8)),
  class = "data.frame", row.names = c(NA, -6L))


f1 <- function(dat, code_nm) {
  dat <- subset(dat,  Code == code_nm)
  
  plot(Numbers ~ Days,  xlim= c(0,45), ylim= c(0,30),
       xaxs='i',data = dat,main = paste0(dmda, "-", code_nm))
  if (var(dat$Numbers)>0){
    
    model <- nls(Numbers ~ b1*Days^2+b2,start = list(b1 = 0,b2 = 0),data = dat, algorithm = "port")
    
    new.data <- data.frame(Days = with(dat, seq(min(Days),max(Days),len = 45)))
    new.data <- rbind(0, new.data)
    lines(new.data$Days,predict(model,newdata = new.data),lwd=2)
    coef<-coef(model)[2]
    points(0, coef, col="red",pch=19,cex = 2,xpd=TRUE)
    text(.99,coef + 1,max(0, round(coef,1)), cex=1.1,pos=4,offset =1,col="black")} else {
      yz <- unique(dat$Numbers)
      lines(c(0,dat$Days), c(yz, dat$Numbers), lwd = 2)
      points(0, yz, col = "red", pch = 19, cex = 2, xpd = TRUE)
      text(.1,yz+ .5,round(yz,1), cex=1.1,pos=4,offset =1,col="black")
    }
  
}

f1(datas, "CDE")

Use mean when it's two points.

m<-mean(datas$Numbers)
> m
[1] 6.416667

For CDE

For ABC

[nirgrahamuk]

Are you asking how to do a horizontal line at a given height ? If so the function is called abline

abline(h=mymean)

Ps.

@JojoSouza

mean<-mean(datas$Numbers)

I strongly recommend against naming results with the same name as an R function

[JojoSouza]

Thanks for the answer @nirgrahamuk ! Probably I have to use the abline function, but how can I this condition, for example, if it's two points or less, use abline function, if it's three points or more, use nls function?

[nirgrahamuk]

@JojoSouza

dat <- subset(dat, Code == code_nm)

if you want to know how many rows there are use nrow
nrow(dat)
you can execute conditional logic with if()/else() structures. You already use if in your code

[JojoSouza]

Thanks for reply @nirgrahamuk . I will try to adjust to see if I can.