try this:
curve(dt(x, 74), from = -4, to = 4)
x <- seq(-1.96, 1.96, len = 100)
y <- dt(x, 74)
polygon(c(x[1], x, x[100]), c(dt(-4, 74), y, dt(4, 74)),
col = "red", border = NA)
I hope it helps.
Best,
Dimitris
----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm
Quoting Chung-hong Chan <[EMAIL PROTECTED]>:
> Dear R experts,
>
> I have plot the PDF of t distribution with df = 74.
> curve(dt(x,df=74),from=-4, to=4)
>
> how can I shade the area under curve (for example, col="red") from
> t=+- 1.996?
>
> Thank you.
> Regards,
> CH
>
> --
> CH Chan
> Research Assistant - KWH
> http://www.macgrass.com
>
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