R作图 Beta Distribution

描述性统计分析的一个实例；贝塔分布

> curve ( dbeta(x, 1, 1), xlim = c(0,1), ylim = c(0,4) )
> curve ( dbeta(x, 3, 1), add = T, col = "green" )
> curve ( dbeta(x, 3, 2), add = T, lty = 2, lwd = 2)
> curve ( dbeta(x, 4, 2), add = T, lty = 2, lwd = 2, col = 'blue' )
> curve ( dbeta(x, 2, 3), add = T, lty = 3, lwd = 3, col = 'red' )
> curve ( dbeta(x, 4, 3), add = T, lty = 3, lwd = 3, col = 'orange' )
> title ( main = "Beta Distribution" )
> legend ( par('usr')[1], par('usr')[4], xjust = 0,
+           c('(1,1)', '(3,1)', '(3,2)', '(4,2)', '(2,3)', '(4,3)'),
+           lwd = c(1, 1, 2, 2, 3, 3),
+           lty = c(1, 1, 2, 2, 3, 3),
+           col = c(par('fg'), 'green', par('fg'), 'blue', 'red', 'orange'))
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curve 简介：

http://127.0.0.1:25686/library/graphics/html/curve.html

Description

Draws a curve corresponding to a function over the interval [from, to]. curve can plot also an expression in the variable xname, default x.

Usage

curve(expr, from = NULL, to = NULL, n = 101, add = FALSE,
      type = "l", xname = "x", xlab = xname, ylab = NULL,
      log = NULL, xlim = NULL, ...)

## S3 method for class 'function'
plot(x, y = 0, to = 1, from = y, xlim = NULL, ylab = NULL, ...)

Arguments

expr	The name of a function, or a call or an expression written as a function of x which will evaluate to an object of the same length as x.
x	a ‘vectorizing’ numeric R function.
y	alias for from for compatibility with plot
from, to	the range over which the function will be plotted.
n	integer; the number of x values at which to evaluate.
add	logical; if TRUE add to an already existing plot; if NA start a new plot taking the defaults for the limits and log-scaling of the x-axis from the previous plot. Taken as FALSE (with a warning if a different value is supplied) if no graphics device is open.
xlim	NULL or a numeric vector of length 2; if non-NULL it provides the defaults for c(from, to) and, unless add = TRUE, selects the x-limits of the plot – see plot.window.
type	plot type: see plot.default.
xname	character string giving the name to be used for the x axis.
xlab, ylab, log, ...	labels and graphical parameters can also be specified as arguments. See ‘Details’ for the interpretation of the default for log. For the "function" method of plot, ... can include any of the other arguments of curve, except expr.