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Formatting POSIXt values in plot axis labels

4 messages · Jason Turner, Ronnen Levinson, Huan Huang +1 more

Original
Jason Turner
#
On Mon, Aug 05, 2002 at 02:23:07PM -0700, Ronnen Levinson wrote:
...
Yup.  In two steps...

1) plot, but without a labeled x-axis (x.stuff should have 
class "POSIXct"):

matplot(x.stuff, y.stuff, xaxt="n")


2) you can now use axis.POSIXct()
And a very nice function it is.  You can tell it where to put
the ticks (if you don't find the defaults appropriate), and what
format to display the dates.

Cheers

Jason
Ronnen Levinson
# 
Hello.

I have an XYY series that I would like to graph with matplot() or some
other single function that will do the trick.
The X in question is a vector of POSIXt values obtained from strptime().

Is it possible to tell matplot() how to handle POSIXt x values?

I have examined the examples at
http://lark.cc.ukans.edu/~pauljohn/R/statsRus.html#5.22 , but would
prefer not have to overlay the results of multiple plot() calls.

Example:

a=strptime("06/01/2002 12:00:00","%m/%d/%Y %H:%M:%S")
x=seq(a,a+10*24*3600,length=3)
y=seq(1,4)
plot(x,y)
matplot(x,cbind(y,y))

I have also noticed that plot() seems to make judgement calls as to how
to present POSIXt values. For example,

a=strptime("06/01/2002 12:00:00","%m/%d/%Y %H:%M:%S")
x=seq(a,a+3*24*3600,length=3)
y=seq(1,4)
plot(x,y)

shows days of week. Is there a way for me to give plot() and/or
matplot() formatting instructions for POSIXt values?

Thanks,

Ronnen.

R1.5.1 on Windows 98

--
Ronnen Levinson, Ph.D.            \/      RML27 at cornell.edu
scientist                         ||      http://ronnen.com
Lawrence Berkeley National Lab    /\      fax 425.955.1992

======================================
Men in colored shirts and seersucker suits, women in slacks and midriff
dresses displaying
various grades of abdomen, moved in and out of California Spanish shops
and office buildings.
Nobody looked at the mountains standing above the town, but the
mountains were there,
making them all look silly.

-- Ross Macdonald, "The Moving Target"
======================================


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Huan Huang
# 
Dear list,

I have done the ridge regression. But it seems the function lm.ridge does
not return the variance for the estimators. Does anyone know how I can work
out the variance for the estimators (my matrix has factors)? Thanks a lot?

Huan

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Frank E Harrell Jr
# 
You can also do ridge regression (penalized least squares) using the ols function in the Design library.  This function provides standard errors but there is not a rich theory that provides complete comfort on their accuracy.

Frank Harrell

On Tue, 6 Aug 2002 10:51:55 +0100
Huan Huang <huang at stats.ox.ac.uk> wrote: