图 13.28 二项分布与泊松分布。

图 13.28 可以用以下 R 代码生成：

k <-0:7 # 二项分布： # 恰好 k 次成功的概率，使用 # 二项分布计算 probability_b<- dbinom(k, prob = 0.1, size=25) # 恰好 k 次成功的概率，使用 # 泊松分布计算 probability_p<- dpois(k, lambda=2.5) plot(k-0.1, probability_b, pch=19, axes=F, col="blue", ylim=c(0,0.3), cex=1.2, cex.axis=2, cex.lab=1.2, xlab=expression(italic(k)), ylab="概率", las=1) points(k+0.1, probability_p, pch=19, col="blue") axis(1, at=seq(0,7,1)) axis(2, at=c(0, 0.1, 0.2, 0.3),las=1) box(bty = "l") abline(h=0, col="blue") for(i in 1:length(k)) { segments(k[i]-0.1, 0, x1 = k[i]-0.1, y1 = probability_b[i], col = "blue", lty = 1, lwd = 2) segments(k[i]+0.1, 0, x1 = k[i]+0.1, y1 = probability_p[i], col = "blue", lty = "dashed", lwd = 1) } points(4.5, 0.29, pch=19, col="blue") segments(4.5, 0.29, 4.5, 0.26, lty=1, lwd=2, col="blue") text(4.6, 0.285, "二项分布，", pos=4) text(4.6, 0.265, expression(paste(italic('n'),' = ', '25', ', ', italic('p'), ' = ', '0.1', sep='')), pos=4) points(4.5, 0.23, pch=19, col="blue") segments(4.5, 0.23, 4.5, 0.20, lty="dashed", lwd=1, col="blue") text(4.6, 0.22, expression(paste('泊松分布', ', ', lambda, ' = ', '2.5', sep='')), pos=4)