Hello,
It is completely normal. I advise you to read the manual "An
introduction to R" on the CRAN website. For example you can find (part
12.1.1) :
12.1.1 The |plot()| function
One of the most frequently used plotting functions in R is the
|plot()| function. This is a /generic/ function: the type of plot
produced is dependent on the type or /class/ of the first argument.
|plot(|x|, |y|)|
|plot(|xy|)|
If x and y are vectors, |plot(|x|, |y|)| produces a scatterplot of y
against x. The same effect can be produced by supplying one argument
(second form) as either a list containing two elements x and y or a
two-column matrix.
|plot(|x|)|
If x is a time series, this produces a time-series plot. If x is a
numeric vector, it produces a plot of the values in the vector
against their index in the vector. If x is a complex vector, it
produces a plot of imaginary versus real parts of the vector elements.
|plot(|f|)|
|plot(|f|, |y|)|
f is a factor object, y is a numeric vector. The first form
generates a bar plot of f; the second form produces boxplots of y
for each level of f.
|plot(|df|)|
|plot(~ |expr|)|
|plot(|y| ~ |expr|)|
df is a data frame, y is any object, expr is a list of object names
separated by `|+|' (e.g., |a + b + c|). The first two forms produce
distributional plots of the variables in a data frame (first form)
or of a number of named objects (second form). The third form plots
y against every object named in expr.
Alain
On 26-Jul-10 13:38, 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
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
--
Alain Guillet
Statistician and Computer Scientist
SMCS - IMMAQ - Université catholique de Louvain
Bureau c.316
Voie du Roman Pays, 20
B-1348 Louvain-la-Neuve
Belgium
tel: +32 10 47 30 50
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