You want to read the help ?segments. Try the following to get the barplots:
ymean=c(1.25,2.65,3.45) ysd=c(0.35,0.65,0.50) xpos=barplot(ymean,ylim=c(0,max(ymean)+max(ysd)),col='yellow') segments(xpos,ymean-ysd,xpos,ymean+ysd) HTH, Rob Baer ----- Original Message ----- From: "Matteo Vidali" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Friday, May 21, 2004 4:03 AM Subject: [R] bars with sd > I need some help for a curious question of a friend of mine. > She usually does some experiments (3-5 repeats for each exp) and then she > calculates mean and standard deviation. > In microsoft excel she writes something like the following > > sample mean sd > a 1.25 0.35 > b 2.65 0.65 > c 3.45 0.50 > > She can do a vertical barplot graph just giving mean value and specifying > the standard deviation value for each bar in the graph. > > My friend wants to know if it is possible to do the same with R. She has > tried also with Open Office and seen that in that program you can plot mean > values as bars but it is not possible to specify a different sd for each > bar 'cause the program, if you ask to put the standard deviation, calculates > a common sd using the mean values. > I was not able to give her an answer for the barplot function in R. I have > just said to her that it is likely due to the fact that using a barplot > graph to plot mean and standard deviation values it is non a good practice, > since the height (or the area) of bars should represent frequency and that > putting a standard deviation in that way it is at least quite confusing for > the reader to interpret the graph. Some scientific journal revisors > discourage this practice. She should instead use a boxplot or just plotting > the different repetition values for each sample as points and add a linea > indicating the mean. > But if this is correct why in some programs like open office you can plot > bars with a common standard deviation???? when will you need this last type > of graph? > > any suggestion? any help? > thanks in advance > Matteo > > ______________________________________________ > [EMAIL PROTECTED] mailing list > https://www.stat.math.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
