**From:** Spencer Graves (*spencer.graves@pdf.com*)

**Date:** Sat 22 May 2004 - 01:15:45 EST

**Next message:**Sean Davis: "Re: [R] bars with sd"**Previous message:**Sean Davis: "Re: [R] Help with hclust() and plot()"**In reply to:**Matteo Vidali: "[R] bars with sd"**Next in thread:**Sean Davis: "Re: [R] bars with sd"**Reply:**Sean Davis: "Re: [R] bars with sd"

Message-id: <40AE1D21.6080406@pdf.com>

* > DF <- data.frame(mean=c(1.25, 2.65, 3.45), sd=c(.35, .65, .5),
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+ row.names=letters[1:3])

* > plot(1:3, DF$mean, ylim=range(DF$mean-2*DF$sd, DF$mean+2*DF$sd))
*

* > segments(1:3, DF$mean-2*DF$sd, 1:3, DF$mean+2*DF$sd)
*

hope this helps. spencer graves

Matteo Vidali wrote:

*>I need some help for a curious question of a friend of mine.
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*>She usually does some experiments (3-5 repeats for each exp) and then she
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*>calculates mean and standard deviation.
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*>In microsoft excel she writes something like the following
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*>
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*>sample mean sd
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*>a 1.25 0.35
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*>b 2.65 0.65
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*>c 3.45 0.50
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*>
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*>She can do a vertical barplot graph just giving mean value and specifying
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*>the standard deviation value for each bar in the graph.
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*>
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*>My friend wants to know if it is possible to do the same with R. She has
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*>tried also with Open Office and seen that in that program you can plot mean
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*>values as bars but it is not possible to specify a different sd for each
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*>bar 'cause the program, if you ask to put the standard deviation, calculates
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*>a common sd using the mean values.
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*>I was not able to give her an answer for the barplot function in R. I have
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*>just said to her that it is likely due to the fact that using a barplot
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*>graph to plot mean and standard deviation values it is non a good practice,
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*>since the height (or the area) of bars should represent frequency and that
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*>putting a standard deviation in that way it is at least quite confusing for
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*>the reader to interpret the graph. Some scientific journal revisors
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*>discourage this practice. She should instead use a boxplot or just plotting
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*>the different repetition values for each sample as points and add a linea
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*>indicating the mean.
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*>But if this is correct why in some programs like open office you can plot
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*>bars with a common standard deviation???? when will you need this last type
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*>of graph?
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*>
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*>any suggestion? any help?
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*>thanks in advance
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*>Matteo
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*>
*

*>______________________________________________
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*>R-help@stat.math.ethz.ch mailing list
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*>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
*

*>PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
*

*>
*

*>
*

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**Next message:**Sean Davis: "Re: [R] bars with sd"**Previous message:**Sean Davis: "Re: [R] Help with hclust() and plot()"**In reply to:**Matteo Vidali: "[R] bars with sd"**Next in thread:**Sean Davis: "Re: [R] bars with sd"**Reply:**Sean Davis: "Re: [R] bars with sd"

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