# Read data (downloaded from https://datadashboard.health.gov.il/COVID-19/general)
# If needed, use setwd() to change directory
library(readxl)
data <- read_excel("daily_new_cases.xlsx", col_names = FALSE, skip = 2)

# First few days
firstDays <- 15:40
dates <-as.Date( data[[1]][firstDays], "%d-%m-%Y" )
cases <-as.numeric( data[[4]][firstDays] )

# Standard plot
plot( dates, cases )

# Logarithmic scale
plot( dates, log(cases) )

# Linear regression
Y <- log(cases)
X <- rbind( firstDays^0, firstDays )
A <- Y %*% t(X) %*% solve( X %*% t(X) )

matplot(dates, A[1] + A[2]*firstDays, type = "l",col="red",add = TRUE )

# what will happen in 3 months?
print( exp(A[1]+A[2]*90) )

# A few more days...
moreDays <- 15:80
dates <-as.Date( data[[1]][moreDays], "%d-%m-%Y" )
cases <-as.numeric( data[[4]][moreDays] )
plot( dates, log(cases) )
matplot(dates, A[1] + A[2]*moreDays, type = "l",col="red",add = TRUE )