[R-SIG-Finance] histogram, sd and mean questions

[Brian G. Peterson]

donahchoo at me.com wrote:
> Hi,
> 
> I'm trying to plot the histogram, sd and mean of some range data I have 
> collected and I have several questions.  First off, my statistics is 
> ancient at best, so if I get things wrong forgive me.
> 
> What I'm trying to do is determine the range of the YM for 30 minute 
> periods throughout the day.  I've got the code the determining range 
> working, but my standard deviation plots appear to be off.
> 
> In the graph below the orange dotted line is the mean and the dotted red 
> lines are +/- 1sd.  What I want to determine what ranges are within 1 sd 
> of the mean and this graph looks off to me.
> 
> Can anyone confirm that I have (not) done this correctly?  Is there a 
> way I can get a finer scale on the x axis? So far I haven't found a way 
> to set tick marks on the charts...
> 
> Here's my R code:
> 
>  > hist(range_tmp, breaks=250, xlim=c(0,250))
>  > abline(v=mean(range_tmp), col='orange', lty=2, lwd=2.5)
>  > abline(v=mean(range_tmp) + sd(range_tmp), col='red', lty=2, lwd=2.5)
>  > abline(v=mean(range_tmp) - sd(range_tmp), col='red', lty=2, lwd=2.5)

I know better than to guess at whether a statistical calculation is correct by 
looking at the graph, and you didn't include your data.

Your code looks fine, without having access to the data to check it.

In the future, please send Stats 101 and R 101 questions to the general r-help 
list, as this has nothing at all to do with finance.

Regards,

     - Brian

-- 
Brian G. Peterson
http://braverock.com/brian/
Ph: 773-459-4973
IM: bgpbraverock