# [R] Boxplot with linear (not categorical) x-axis

Luigi Marongiu m@rongiu@luigi @ending from gm@il@com
Mon Oct 1 08:44:01 CEST 2018

```Thank you.
On Fri, Sep 28, 2018 at 5:34 PM William Dunlap <wdunlap using tibco.com> wrote:
>
> Use the 'at' argument to boxplot.  E.g.,
>
> > x <- rep(c(2,4,8,16), c(5,10,20,30))
> > y <- seq_along(x)
> > par(mfrow=c(2,1))
> > boxplot(y~x, at=unique(x))
> > boxplot(y~x)
>
>
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
> On Fri, Sep 28, 2018 at 3:05 AM, Luigi Marongiu <marongiu.luigi using gmail.com> wrote:
>>
>> Dear all,
>> I am using boxplot to draw some data. Would be possible to have the
>> X-axis linear (as in a scatter plot) instead of the standard
>> categorical axis?
>> The data I have is subdivided into three groups at the numerical
>> values 1, 3, 5; boxplot treats these as categorical values; in fact, I
>> can write my own labels simply by using the values 1, 2, 3 for the
>> position of the labels as in the example.
>> Thank you,
>>
>> >>>>
>> # generate data.frames
>> A = c(70, 22, 4, 21, 29, 35, 24, 20, 9, 21,
>>       22, 12, 20, 21, 13, 18, 15, 3, 9, 23,
>>       6, 5, 2, 24, 25, 21, 16, 0, 4, 1)
>> B = c(17, 21, 70, 6, 23, 10, 8, 5, 22, 5,
>>       21, 5, 19, 9, 23, 24, 11, 13, 7, 15,
>>       25, 9, 13, 14, 11, 9, 12, 0, 5, 9)
>> C = c(17, 8, 30, 22, 11, 32, 33, 8, 160, 11,
>>       35, 7, 36, 15, 11, 25, 16, 6, 38, 19,
>>       35, 30, 12, 27, 22, 32, 47, 39, 31, 26)
>> X = rep(c(1, 3, 5),30*3)
>> dfA <- data.frame(X, c(A, B, C))
>> names(dfA) <- c("X", "Y")
>> par(mfrow=c(2,1))
>> boxplot(dfA\$Y ~ dfA\$X,
>>         ylim=c(0, 80),
>>         col="green",
>>         ylab="Y-values",
>>         xlab="X-values",
>>         main="usual X labels"
>> )
>> boxplot(dfA\$Y ~ dfA\$X,
>>         ylim=c(0, 80),
>>         col="green",
>>         ylab="Y-values",
>>         xlab="X-values",
>>         main="custom X labels",
>>         xaxt="n"
>> )
>> x.lab = c("A", "B", "C")
>> x.pos = c(1, 2, 3)
>> axis(side=1, at=x.pos,
>>      lab=x.lab, cex.axis=1)
>>
>> --
>> Best regards,
>> Luigi
>>
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