library(DBI)
library(odbc)
con <- dbConnect(odbc(), 
                 Driver = "ODBC Driver 17 for SQL Server", 
                 Server = "REX\\SQLEXPRESS", 
                 Database = "VYUKA_DATABAZE", 
                 Trusted_Connection="yes",
                 encoding = "CP1250")
dbListTables(con)
data<-dbGetQuery(con,"
SELECT * 
FROM [dbo].[nakaza_po_dnech] ('2020-08-01','2021-03-31')
order by my_order,datum
")

data$active_cases<-cumsum(data$nakaza-data$umrti-data$vyleceni)
data$active_cases[data$my_order!=1]<-NA
plot(data$datum,data$active_cases,type = 'l',xlab="datum",ylab="active cases")

data.1<-data[data$datum<as.Date('2020-10-30') & !is.na(data$datum),]
plot(data.1$datum,data.1$active_cases,type = 'l',xlab="datum",ylab="active cases")
plot(data.1$datum,log(data.1$active_cases),type = 'l',xlab="datum",ylab="log active cases")

x<-1:dim(data.1)[1]
y<-log(data.1$active_cases)
reg<-lm(y~x)
reg$coefficients
plot(data.1$datum,data.1$active_cases,type = 'l',xlab="datum",ylab="active cases")
lines(data.1$datum,exp(reg$coefficients[1]+reg$coefficients[2]*x),col='red',lwd=2)
par(mfrow=c(2,2))
plot(reg)
par(mfrow=c(1,1))