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How can I put error bars on a barplot() ?
2 messages · Olivier BUHARD, Marc Schwartz
On Tue, 2003-12-23 at 08:04, olivier wrote:
Hi all, I am a relatively new R user... trying to put error bars (from SD values) on my data represented with barplot(). But I can't find any function or instruction to do so. Is there an easier way to do this than using segments() as I saw in an example in the R reference manual ? Then, can I define there graphical apparence ? Thanks for help. Regards Olivier BUHARD
Olivier, You can use either segments() or arrows() to place error bars on barplots. Also, there is barplot2() in the gregmisc package on CRAN, which provides this functionality and enables you to pass the error bar values as arguments to the function. As you may have noted, if you use either segments() or arrows(), the key is to get the bar midpoints for proper line placement. The bar midpoints are returned from the barplot() function and that is described in the help for barplot(). If you should elect to use barplot2(), let me know if you have any questions on its use. Best regards, Marc Schwartz