[R] I want axes that cross

[Paul Johnson]

On Fri, Feb 13, 2009 at 1:51 PM, Marc Schwartz
<marc_schwartz at comcast.net> wrote:
> on 02/13/2009 01:25 PM Paul Johnson wrote:
>> Hello, everybody.
>>
>> A student asked me a howto question I can't answer.  We want the
>> length of the drawn axes to fill the full width and height of the
>> plot, like so:

> Paul,
>
> I am guessing that you want:
>
> x <- rnorm(100)
> z <- gl(2,50)
> y <- rnorm(100, mean= 1.8*as.numeric(z))
>
> plot(x,y,type="n", axes=F)
> points(x,y, pch="$",cex=0.7, col=z)
> axis(1, col="green", col.axis="green")
> axis(2, col="red", col.axis="red")
>
> # Draw the box like an "L" on the bottom and left only
> box(bty = "l")
>
>
> Note that you can specify which sides the 'box' is created upon by using
> the 'bty' argument. See ?box for more information.

Thanks, I did not find bty under ?box, but found it under par after
you pointed it out.

That does not get the correct output, however, because the black box
covers over my 2 different colored axes.

Even if I weren't color-conscious, it gives me this:

|
|
|_______

not crossed axes, which I want:

   |
   |
 _|______
   |

I'm putting in a seed so we will both see the same things in this example.

set.seed(1233240)
x <- rnorm(100)
z <- gl(2,50)
y <- rnorm(100, mean= 1.8*as.numeric(z))
plot(x,y,type="n", axes=F)
points(x,y, pch="$",cex=0.7, col=z)
axis(1, col="green", col.axis="green")
axis(2, col="red", col.axis="red")

# MS recomends:
 # Draw the box like an "L" on the bottom and left only
 box(bty = "l")

>
> Also, by default, the axes extend the range of 'x' and 'y'  by 4%. You
> can use 'xaxs = i' and 'yaxs = i' in the plot() call to restrict the
> axes to the true ranges of 'x' and 'y'.  This would be important, for
> example, when you want the lower left hand corner of the plot to be at
> exact coordinates such as 0,0.

I would be delighted if the axes really did reach 4% outside the data.
But they don't.  I've seen that same thing you are referring to in the
documentation, but there's something wrong about it, In my example
code, we should see the same thing now I've put in a seed. The axes
are smaller than the data range, not equal to 1.04 times the data
range. I see several observations in the graph that are "off the
charts", they are above the highest value of the y axis, or below the
lowest axis value. Similarly, there are observations smaller than the
low end of the x axis and bigger than the largest x axis value.

The 4% may be the plot region's size, but it is surely not the length
of the axis that is drawn?

>
> See ?par for more information.
>
> HTH,
>
> Marc Schwartz
>
>



-- 
Paul E. Johnson
Professor, Political Science
1541 Lilac Lane, Room 504
University of Kansas