[R] Plot means with error bars - A novice needs help

Jim Lemon jim at bitwrit.com.au
Thu Oct 9 10:54:09 CEST 2008

Michael Just wrote:
> Thank you all for you suggestions. They are all helpful. However, I 
> have come to a more fundamental problem. Preparing my data to even 
> make such a graph. I thought I was ready.  I will obviously need to 
> find the n, mean, and confidence interval for my data before I can 
> plot them. for some of these plots.
> I thought perhaps this data manipulation would be easily done in R, 
> but perhaps I should do it elsewhere and then bring it into R. I have 
> about 5000 rows & about 30 columns in my csv. I need to find: mean, n, 
> confidence interval for a to-be-made selection from the entire data set.
> I have tried: aggregate, subset, dat$col1=2, etc
> Clearer?: I want to select data from my dataset where column1=2. Then 
> when plotting this data I want to group it by 2 values (out of 4) from 
> column10.
Hi Michael,
The describe function in the prettyR package might get the summaries you 
want. I think you want to set num.desc=c("mean","std.error","valid.n"). 
Combine describe with the "by" function to perform the subsetting, and 
you should get what you want.


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