R help - Feb 2008 - Why does plot() ignore the data type for axis labels?

Hello,

I was wondering why the plot() command ignores the datatype when displaying
axis labels.  More specifically, if the data points are integers then the
axis labels should intuitively also be integers, right?
> x <- as.integer(c(1,2,3))
> y <-x
> typeof(x)
[1] "integer"
> plot(x,y)
>
The axis labels are 1.0, 1.5, 2.0, 2.5, 3.0  but if the integer type were
taken into account they would be 1, 2, 3.

PS what's the right way to get integer labels?
Z.
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I don't do "why" answers. Only how. Occasionally.

?plot.default  ##with the axes=FALSE argument. Then

?axis ## note the labels and at arguments.



Bert Gunter
Genentech Nonclinical Statistics


-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of Stiffler
Sent: Tuesday, February 19, 2008 9:18 AM
To: r-help at r-project.org
Subject: [R] Why does plot() ignore the data type for axis labels?


Hello,

I was wondering why the plot() command ignores the datatype when displaying
axis labels.  More specifically, if the data points are integers then the
axis labels should intuitively also be integers, right?
> x <- as.integer(c(1,2,3))
> y <-x
> typeof(x)
[1] "integer"
> plot(x,y)
>
The axis labels are 1.0, 1.5, 2.0, 2.5, 3.0  but if the integer type were
taken into account they would be 1, 2, 3.

PS what's the right way to get integer labels?
Z.
-- 
View this message in context:
http://www.nabble.com/Why-does-plot%28%29-ignore-the-data-type-for-axis-labe
ls--tp15562325p15562325.html
Sent from the R help mailing list archive at Nabble.com.

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On Tue, 2008-02-19 at 09:17 -0800, Stiffler wrote:
> Hello,
> 
> I was wondering why the plot() command ignores the datatype when displaying
> axis labels.  More specifically, if the data points are integers then the
> axis labels should intuitively also be integers, right?
> 
> > x <- as.integer(c(1,2,3))
> > y <-x
> > typeof(x)
> [1] "integer"
> > plot(x,y)
> >
> 
> The axis labels are 1.0, 1.5, 2.0, 2.5, 3.0  but if the integer type were
> taken into account they would be 1, 2, 3.
It is due to pretty() finding nice numbers for the axis
> pretty(x)
[1] 1.0 1.5 2.0 2.5 3.0
> 
> PS what's the right way to get integer labels?
Do them by hand, if they are (numeric) integers
> plot(x,y, axes = FALSE)
> axis(2)
> axis(1, at = x)
> box()
You could try writing your own Axis.integer function if doing the extra
steps is a pain - something like:

Axis.integer <- function(x = NULL, at = NULL, ..., side, labels = NULL) 
{
    at <- unique(x)
    labels <- as.character(at)
    axis(side = side, at = unique(x), labels = labels, ...)
}

which works in these case,

y2 <- runif(3)
plot(x, y)
plot(x, y2)

But is far from bullet proof and is not guaranteed to work in all
situations.

HTH

G

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Hi Stiffler,
>> I was wondering why the plot() command ignores the datatype when
>> displaying axis labels...
plot() doesn't ignore the datatype:
> x <- as.integer(c(1,2,3))
> y <-x
> typeof(x)
[1] "integer"
> mode(x)
[1] "numeric"

plot(x,y) calls xy.coords(), which recasts x as: x = as.double(x), which is
fine, since x is (also/primarily) numeric.

???

See ?double, sub: "Note on names".

HTH, Mark.



Stiffler wrote:
> 
> Hello,
> 
> I was wondering why the plot() command ignores the datatype when
> displaying axis labels.  More specifically, if the data points are
> integers then the axis labels should intuitively also be integers, right?
> 
>> x <- as.integer(c(1,2,3))
>> y <-x
>> typeof(x)
> [1] "integer"
>> plot(x,y)
>>
> 
> The axis labels are 1.0, 1.5, 2.0, 2.5, 3.0  but if the integer type were
> taken into account they would be 1, 2, 3.
> 
> PS what's the right way to get integer labels?
> Z.
> 
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