[R] barplot2 x-axis

Mafalda Viana vianam at tcd.ie
Sun Mar 22 22:45:04 CET 2009

Dear Mark,

Thanks for your reply.

I attach one of my plots as an example (e.g.Mafalda) to show what I want. If
you notice in the plot the x-axis has a funny scale (0, 13, 28...) and what
I would like to do is to make that scale from 0 and then increasing by 25 km
for a better interpretation (0, 25, 50...).

Hopefully my problem is more clear now, meanwhile I will have a look to your

Thank you very much

2009/3/22 Marc Schwartz <marc_schwartz at comcast.net>

>  On Mar 22, 2009, at 2:31 PM, Mafalda Viana wrote:
> Dear R users,
>> I am trying to build a barplot2 graph however I can't find a way of
>> defining
>> the scale for the x-axis.
>> I would like to show in my x-axis only the numbers 0, 25, 50, 75 etc. (so
>> far R is giving me a random scale hard to interpret and it doens't look
>> nice...). Could anyone advise me on how to do this please, it would be a
>> great help! Thank you.
>> Below I show the code I have been using for my plots.
>> my.plot<- barplot2(mydata.y, names.arg=mydata.x, width=1,
>> xlab="km", ylab="kg", main="plot.name",
>> plot.ci=TRUE, ci.l=data.lci,ci.u=data.uci, ci.col = "red", font=40,
>> font.lab=60, xlim=c(0,250), xpd=FALSE)
> It is not entirely clear what you are doing here an we cannot reproduce it
> lacking your data.
> Your x (horizontal) axis will have one tick mark below each bar, using the
> labels that you have indicated with mydata.x. Based upon your code, the x
> axis values would appear to be measures of distance.
> Your y (vertical) axis would appear to be a measure of weight, perhaps
> being some descriptive statistic (eg. mean) for weight at each distance.
> It is unclear what you want to do with the x axis in lieu of the default
> values. Modifying the tick marks on the y axis would seem to make more sense
> here.
> In general, with any R graphic, you would use the arguments 'xaxt = "n"'
> and/or 'yaxt = "n"' to disable the default drawing of the x and y axes,
> respectively. You would then call the axis() function passing the specific
> locations and values of the tick marks that you wish to draw. See ?par and
> ?axis for more information on these.
> BTW if you are not plotting counts or proportions/percentages, then a
> barplot is not the best approach for the display of summarized continuous
> data. I would use a point plot with error bars/confidence intervals. See the
> errbar() function in the Hmisc package or the plotCI() or plotmeans()
> functions in gplots. You could also create something manually by using
> plot() and then either segments() or arrows() for the CIs.
> HTH,
> Marc Schwartz

Mafalda Viana

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