# Emprical Cumulative Distribution Function (ECDF)

### Description

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.

### Usage

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### Arguments

`xx` |
name of the variable to be plotted. |

`xlab` |
by default the character string for |

`ylab` |
a title for the y-axis, defaults to |

`log` |
to display the data with logarithmic (x-axis) scaling, set |

`xlim` |
when used in the |

`main` |
when used stand-alone a title may be added optionally above the plot by setting |

`pch` |
by default the plotting symbol is set to a plus, |

`ifqs` |
setting |

`cex` |
by default the size of the text for data set size, N, is set to 80%, i.e. |

`...` |
further arguments to be passed to methods. The colour of the plotting symbols may be changed from default blach, e.g., |

### Note

Any less than detection limit values represented by negative values, or zeros or other numeric codesrepresenting blanks in the data, 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)`

, the latter being appropriate for a logarithmically scale plot, i.e. `log = TRUE`

. 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.

The available symbols are:

pch: 0 = square, 1 = circle, 2 = triangle, 3 = plus, 4 = X,

5 = diamond, 6 = upside-down triangle, 7 = square with X,

8 = asterisk, 9 = diamond with plus, 10 = circle with plus,

11 = double triangles, 12 = square with plus,

13 = circle with X, 14 = square with upside-down triangle.

Symbols 15 to 18 are solid in the colour specified:

15 = square, 16 = circle, 17 = triangle, 18 = diamond.

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`

.

### Author(s)

Robert G. Garrett

### See Also

`display.marks`

, `ltdl.fix.df`

, `remove.na`

### Examples

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