Make condition for graph generation when there are two points

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
enter image description here

For ABC

enter image description here

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

abline(h=mymean)

Ps.

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

1 Like

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?

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

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