On 12/11/2010 02:25 AM, Simon Kiss wrote:
Dear colleagues,
i found a line or two of code in the help archives from Uwe Ligges about 
creating slanted x-labels for a barplot and it works well for my purposes (code 
below). However, I was hoping someone could explain to me precisely what the 
code is doing.
I'm aware it's invoking the text command, and I know the first ttwo arguments to text are x and y co-ordinates.  I'm 
also aware that par("usr")[3] is grabbing the third element of the vector of plotting co-ordinates.  But I 
tried replacing par("usr")[3] with just "0" and that didn't work; all the labels got bunched up on 
the left.  Is it necessary to create a new object via "barplot" and then quote that in the x,y coordinates of 
text?
Like I said, the code works great, but I'm trying to actually understand the 
rationale behind the elements so I can apply it in future.

Hi Simon,
The staxlab function will add an axis to an existing plot with either staggered or rotated labels. It is somewhat similar to Uwe's function. Looking at both the code and the examples on the help page might give you some idea why the function was written. It is principally to allow the user to add more labels than would be displayed on the default axes, and to decide whether staggering or rotating those labels will produce a better looking plot. The problem most often mentioned in adding custom labels to a plot produced by barplot is that the bars are centered on non-integer values, and so the user must get the return value of barplot and use that for the axis label positions.

Jim

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