R help - Jan 2003 - Fw: Plotting text-string real_date names at excel_date positions.

How do I post text-string dates along the x-axis instead of the excel_date
position values?

I would like to plot a time-series of chemical values changing with time
The first column is the internal date from excel.  This should be the x-axis
position of a graph
of the plotted data.

The second column is a text-string of date.  This should be what is posted
(instead of the excel_date).
The third column is the chemical data and this should be the position of a
point on the y-axis.
A line needs to connect the points but should break at the NA.

excel_date    real_date        chemical
36234        15-Mar-99        1.6
36302        22-May-99        0.195
36395        23-Aug-99        4.9
36475        11-Nov-99        NA
36593        8-Mar-00          3.58

Rex

You probably want to use the `axes = FALSE' argument to plot and then
construct the axes yourself with the axis() function.  Perhaps something
like (using the real variable names, of course):

attach("mydataset")
plot(exceldate, chemical, axes = FALSE, frame.plot = TRUE, type = "l")
axis(2)
axis(1, exceldate, realdate)

This may produce an x-axis that's too crammed so you'll have to fiddle
with it so that the labels are nicely spaced.  Maybe something like

idx <- seq(1, length(exceldate), by = 2)
axis(1, exceldate[idx], realdate[idx])

-roger
_______________________________
UCLA Department of Statistics
rpeng at stat.ucla.edu
http://www.stat.ucla.edu/~rpeng

On Sun, 12 Jan 2003, Rex_Bryan at urscorp.com wrote:
> How do I post text-string dates along the x-axis instead of the excel_date
> position values?
> 
> I would like to plot a time-series of chemical values changing with time
> The first column is the internal date from excel.  This should be the
x-axis
> position of a graph
> of the plotted data.
> 
> The second column is a text-string of date.  This should be what is posted
> (instead of the excel_date).
> The third column is the chemical data and this should be the position of a
> point on the y-axis.
> A line needs to connect the points but should break at the NA.
> 
> excel_date    real_date        chemical
> 36234        15-Mar-99        1.6
> 36302        22-May-99        0.195
> 36395        23-Aug-99        4.9
> 36475        11-Nov-99        NA
> 36593        8-Mar-00          3.58
> 
> Rex
> 
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