[R] CI wiskers

[Steve Lianoglou]

Hi,

On Jul 24, 2009, at 11:43 AM, Dieter Menne wrote:

> mfreidin wrote:
>>
>> I have a matrix containing means and CIs (lower and upper in two  
>> columns,
>> so three columns for every data point) for several points. I have  
>> to build
>> a graph of these means accompained by the CIs (as wiskers). No  
>> problems
>> with making the graph of means, but I don't know how to introduce  
>> CIs.
>>
>
> xYplot in package Hmisc (not the uppercase Y)

Rolling your own isn't all that difficult either (especially when  
someone else has written such a function already :-).

This code was lifted straight out of lars package (called when  
plotting CV error):

error.bars <- function (x, upper, lower, width = 0.02, ...) {
     xlim <- range(x)
     barw <- diff(xlim) * width
     segments(x, upper, x, lower, ...)
     segments(x - barw, upper, x + barw, upper, ...)
     segments(x - barw, lower, x + barw, lower, ...)
     range(upper, lower)
}

``x`` is the x positions you want to draw the whiskers
``upper`` is a vector of length x and indicates the top of the whisker  
at each x
``lower`` is a vector of length x and indicates the bottom of the  
whisker at each x
``width`` is the length of the "hat" to put at each whisker (typically  
1/x works well here, too)

HTH,
-steve

--
Steve Lianoglou
Graduate Student: Computational Systems Biology
   |  Memorial Sloan-Kettering Cancer Center
   |  Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact