Data source: WHO Situation reports

Curve estimates using **R** (Link to free download) with prediction intervals using the `propagate`

package. Code below (quick note – `propogate`

function not necessary for this figure, but generates 95% prediction intervals [only means are shown on graph], but prediction intervals will be displayed if you run code):

`library(propagate)`

`par(family="serif")`

`Y <- c(282, 314, 581, 846, 1320, 2014, 2798, 4593, 6065, 7818, 9826,`

`11953, 14557, 17391, 20630, 24554, 28276, 31532, 34878)`

`n <- as.numeric(length(Y))`

`temp <- data.frame(y = Y, x = seq(1:n))`

`# Exponential and Logistic (sigmoid) functions`

`mod <- nls(y ~ exp(a + b * x), data = temp, start = list(a = 0, b = 1))`

`Z <- nls(y ~ SSlogis(x, Asym, xmid, scal), temp)`

`BIC(mod, Z)`

`(PROP1 <- predictNLS(mod, newdata = data.frame(x = c(n+1, n+2, n+3)), interval = "prediction"))`

`(PROP2 <- predictNLS(Z, newdata = data.frame(x = c(n+1, n+2, n+3)), interval = "prediction"))`

`az<-as.data.frame(rbind(PROP2$prop[[1]]$sim[1],`

`PROP2$prop[[2]]$sim[1],`

`PROP2$prop[[3]]$sim[1]))`

`bz<-as.data.frame(rbind(PROP1$prop[[1]]$sim[1],`

`PROP1$prop[[2]]$sim[1],`

`PROP1$prop[[3]]$sim[1]))`

`plot(temp$x, temp$y, ylab = "Confirmed cases", xlab="", xlim=c(0,n+3),`

`ylim=c(0,65000),`

`col="navy", lwd=2, axes=F,`

`main = "Coronavirus confirmed cases (updated 2/08 ~ early numbers)",`

`sub = "BIC(Exponential) = 342.6`

`BIC(Logistic) = 292.9`

`(smaller is better fit)")`

`axis(2)`

`axis(1, at=c(1, n, n+3), lab=c("1/21", "2/08", "2/11"))`

`lines(seq(1:n), predict(mod, list(x = seq(1:n))), lty=2, lwd=2, col='red')`

`lines(seq(1:n), predict(Z, list(x = seq(1:n))), lty=2, lwd=2)`

`text(14, 32000, "34,878 total cases as`

`of Saturday morning")`

`lines(c(n+1, n+2, n+3),az$Mean, col="black", lwd=2)`

`lines(c(n+1, n+2, n+3),bz$Mean, col="red", lwd=2)`

`arrows(11, 50000, 18,50000)`

`text(15, 47000, "3-day forecast for each model")`

`legend(1, 60000, legend=c("Exponential", "Logistic (sigmoid)"),`

`col=c("red", "black"), lty=2)`