[R] sciplot question
Jarle Bjørgeengen
jarle at bjorgeengen.net
Sun May 24 15:52:45 CEST 2009
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
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