[R] sciplot question

[Jarle Bjørgeengen]

On May 24, 2009, at 3:34 , Frank E Harrell Jr wrote:

> Jarle Bjørgeengen wrote:
>> Great,
>> thanks Manuel.
>> Just for curiosity, any particular reason you chose standard  
>> error , and not confidence interval as the default (the naming of  
>> the plotting functions associates closer to the confidence  
>> interval .... ) error indication .
>> - Jarle Bjørgeengen
>> On May 24, 2009, at 3:02 , Manuel Morales wrote:
>>> You define your own function for the confidence intervals. The  
>>> function
>>> needs to return the two values representing the upper and lower CI
>>> values. So:
>>>
>>> qt.fun <- function(x) qt(p=.975,df=length(x)-1)*sd(x)/ 
>>> sqrt(length(x))
>>> my.ci <- function(x) c(mean(x)-qt.fun(x), mean(x)+qt.fun(x))
>
> Minor improvement: mean(x) + qt.fun(x)*c(-1,1) but in general  
> confidence limits should be asymmetric (a la bootstrap).

Thanks,

if the date is normally distributed , symmetric confidence interval  
should be ok , right ?

When plotting the individual sample , it looks normally distributed.

Best regards.
Jarle Bjørgeengen