On Jul 26, 2010, at 7:38 AM, Steffen Uhlig wrote:
Hello,
my data.frame is sort of a collection of process values, i.e. huge
run-chart. It consists of a time-stamp in the first column (date as
string), factors in the following columns (used for subset-
filtering), and some process-data columns.
Hereafter, two examples are listed, showing the problems that occour
during print:
At first the example, that works fine:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
a = c(1:10) # create a vector of integers
b = rep(c("a","b"),5) # create a vector of chars, used
# as factor-levels
d = rnorm(10) # some random numbers
e = data.frame(a,b,d) # connect to a data.frame
You've gotten several answers, but none have addressed an aspect of R
behavior that took me longer to appreciate than it perhaps should
have. The "b" column inside the "e" data.frame is now a factor column.
I mention that because you later referred to it as a "string" which it
is not. It is an integer with an associated indexed level character
vector. Many of the functions that you might think would "work" on
"strings" will give either errors or unexpected results when applied
to factors.
e.1 = subset(e, b=="a") # create two subsets
e.2 = subset(e, b=="b")
plot(d~a, e.1, pch=3, col=2) # plot first data-subset
points(d~a, e.2, pch=4, col=3) # plot the 2nd one
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
all looks fine in theses plots.
However, changing the content of vector "a" to a set of strings the
following happens:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
a = c("a","b","c","d","e","f","g","h","i","j")
e = data.frame(a,b,d) # re-build data.frame
e.1 = subset(e, b=="a") # create two subsets
e.2 = subset(e, b=="b")
plot(d~a, e.1, pch=3, col=2)
points(d~a, e.2, pch=4, col=3)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The plot-command produces horizontal lines instead of dots. This
seems to happen when the x-axis contains strings rather than
numbers. is there a way out?
Best regards,
/Steffen
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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