[英]Plotting the normal and binomial distribution in same plot
正如标题所示,我正在尝试使用 R 在同一图中绘制正态分布和二项式分布。我的尝试如下所示,是否有任何原因为什么我的正态分布看起来如此偏离? 我已经仔细检查了平均值和标准偏差,一切看起来都很好。
n <- 151
p <- 0.2409
dev <- 4
mu <- n*p
sigma <- sqrt(n*p*(1 - p))
xmin <- round(max(mu - dev*sigma,0));
xmax <- round(min(mu + dev*sigma,n))
x <- seq(xmin, xmax)
y <- dbinom(x,n,p)
barplot(y,
col = 'lightblue',
names.arg = x,
main = 'Binomial distribution, n=151, p=.803')
range <- seq(mu - dev*sigma, mu + dev*sigma, 0.01)
height <- dnorm(range, mean = mu, sd = sigma)
lines(range, height, col = 'red', lwd = 3)
barplot
只是您案例的错误功能。 或者,如果您真的想使用它,则必须重新调整barplot
和lines
之间的 x 轴
barplot
的默认值是将每个height
值放在
head(c(barplot(y, plot = FALSE)))
# [1] 0.7 1.9 3.1 4.3 5.5 6.7
这可以通过您选择的space
和width
或两者的组合来改变
head(c(barplot(y, plot = FALSE, space = 0)))
# [1] 0.5 1.5 2.5 3.5 4.5 5.5
head(c(barplot(y, plot = FALSE, space = 0, width = 3)))
# [1] 1.5 4.5 7.5 10.5 13.5 16.5
你可以使用plot
来避免处理这些事情
n <- 151
p <- 0.2409
dev <- 4
mu <- n*p
sigma <- sqrt(n*p*(1 - p))
xmin <- round(max(mu - dev*sigma,0));
xmax <- round(min(mu + dev*sigma,n))
x <- seq(xmin, xmax)
y <- dbinom(x,n,p)
plot(x, y, type = 'h', lwd = 10, lend = 3, col = 'lightblue',
ann = FALSE, las = 1, bty = 'l', yaxs = 'i', ylim = c(0, 0.08))
title(main = sprintf('Binomial distribution, n=%s, p=%.3f', n, p))
lines(x, dnorm(x, mean = mu, sd = sigma), col = 'red', lwd = 7)
xx <- seq(min(x), max(x), length.out = 1000)
lines(xx, dnorm(xx, mean = mu, sd = sigma), col = 'white')
此图中的“条”取决于您选择的lwd
和您的设备尺寸,但如果您需要更好地控制它,您可以使用rect
,这需要更多的工作。
w <- 0.75
plot(x, y, type = 'n', ann = FALSE, las = 1, bty = 'l', yaxs = 'i', ylim = c(0, 0.08))
rect(x - w / 2, 0, x + w / 2, y, col = 'lightblue')
lines(xx, dnorm(xx, mean = mu, sd = sigma), col = 'red', lwd = 3)
title(main = sprintf('Binomial distribution, n=%s, p=%.3f', n, p))
您可以使用ggplot2
包
library(ggplot2)
n <- 151
p <- 0.2409
mean <- n*p
sd <- sqrt(n*p*(1-p))
binwidth <- 0.005
xmin <- round(max(mu - dev*sigma,0));
xmax <- round(min(mu + dev*sigma,n))
x <- seq(xmin, xmax)
y <- dbinom(x,n,p)
df <- cbind.data.frame(x, y)
ggplot(df, aes(x = x, y = y)) +
geom_bar(stat="identity", fill = 'dodgerblue3')+
labs(title = "Binomial distribution, n=151, p=.803",
x = "",
y = "") +
theme_minimal()+
# Create normal curve, akousting for number of observations and binwidth
stat_function(
fun = function(x, mean, sd, n, bw){
dnorm(x = x, mean = mean, sd = sd)
}, col = "red", size=I(1.4),
args = c(mean = mean, sd = sd, n = n, bw = binwidth))
您可以使用ggplot2
包来做到这ggplot2
(我对正态分布感到惊讶,但用 geom_point 替换 geom_line 说服我具有这种形式(方差是否太高?)):
n <- 151
p <- 0.2409
dev <- 4
mu <- n*p
sigma <- sqrt(n*p*(1 - p))
xmin <- round(max(mu - dev*sigma,0));
xmax <- round(min(mu + dev*sigma,n))
x <- seq(xmin, xmax)
y <- dbinom(x,n,p)
z <- dnorm(x = qnorm(p = seq(0,1, length.out = length(x)), mean = mu, sd = sigma), mean = mu, sd = sigma)
library(magrittr)
library(ggplot2)
data.frame(x, y, z) %>%
ggplot(aes(x = x)) +
geom_col(aes(y = y)) +
geom_line(aes(x = x, y = z, colour = "red"),
show.legend = FALSE)
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