gx.ecdf {rgr} | R Documentation |
Displays an empirical cumulative distribution function (ECDF) plot with a zero-to-one linear y-scale as part of the multi-panel display provided by shape
. The function may also be used stand-alone.
gx.ecdf(xx, xlab = deparse(substitute(xx)), ylab = "Empirical Cumulative Distribution Function", log = FALSE, xlim = NULL, main = " ", pch = 3, ifqs = FALSE)
xx |
name of the variable to be plotted. |
xlab |
a title for the x-axis. It is often desirable to replace the default x-axis title of the input variable name text string with a more informative title, e.g., xlab = "Cu (mg/kg) in <2 mm O-horizon soil" . |
ylab |
a title for the y-axis, defaults to "Emprical Cumulative Distribution Function". |
log |
if it is required to display the data with logarithmic (x-axis) scaling, set log = TRUE . |
xlim |
when used in the shape function, xlim is determined by gx.hist and used to ensure all four panels in shape have the same x-axis scaling. However, when used stand-alone the limits may be user-defined by setting xlim , see Note below. |
main |
when used stand-alone a title may be added optionally above the plot by setting main , e.g., main = "Kola Project, 1995" . |
pch |
by default the plotting symbol is set to a plus, pch = 3 , alternate plotting symbols may be chosen from those displayed by display.marks . |
ifqs |
setting ifqs = TRUE results in horizontal and vertical dotted lines being plotted at the three central quartiles and their values, respectively. |
Any less than detection limit values represented by negative values, or zeros or other numeric codesrepresenting blanks in the data vector, must be removed prior to executing this function, see ltdl.fix.df
.
Any NA
s in the data vector are removed prior to displaying the plot.
Although the cumulative normal percentage probability (CPP) plot is often the preferred method for displaying the cumulative data distribution as it provides greater detail for inspection in the tails of the data, the ECDF is particularly useful for studying the central parts of data distributions as it has not been compressed to make room for the scale expansion in the tails of a cumulative normal percentage probability (CPP) plot.
If the default selection for xlim
is inappropriate it can be set, e.g., xlim = c(0, 200)
or c(2, 200)
. If the defined limits lie within the observed data range a truncated plot will be displayed. If this occurs the number of data points omitted is displayed below the total number of observations.
If it is desired to prepare a display of data falling within a defined part of the actual data range, then either a data subset can be prepared externally using the appropriate R syntax, or xx
may be defined in the function call as, for example, Cu[Cu < some.value]
which would remove the influence of one or more outliers having values greater than some.value
. In this case the number of data values displayed will be the number that are <some.value
.
Robert G. Garrett
display.marks
, ltdl.fix.df
, remove.na
## Make test data available data(kola.o) attach(kola.o) ## Plot a simple ECDF gx.ecdf(Cu) ## Plot an ECDF with more appropriate labelling and with the quartiles ## indicated gx.ecdf(Cu , xlab = "Cu (mg/kg) in <2 mm O-horizon soil", log = TRUE, ifqs = TRUE) ## Detach test data detach(kola.o)