chrBreakpoints {GLAD} | R Documentation |

The function `chrBreakpoints.profileCGH`

find breakpoints corresponding to an abrupt change of the DNA amount along the chromosome.

chrBreakpoints.profileCGH(profileCGH, smoothfunc="aws", base=TRUE, sigma, bandwidth=10, round=2, verbose=FALSE, ...)

`profileCGH` |
Object of class "profileCGH". |

`smoothfunc` |
Type of function used to smooth `LogRatio` by a piecewise constant function. Choose either `aws` or `laws` . |

`base` |
If TRUE, the position of BAC is the physical position onto the chromosome, otherwise the rank position is used. |

`sigma` |
Value to be passed to either argument `sigma2`
of` aws` function or `shape` of
`laws` . If `NULL` , sigma is calculated from
the data. |

`bandwidth` |
Set the maximal bandwidth `hmax` in the
`aws` or `laws` function. For
example, if `bandwidth=10` then the `hmax` value is set
to 10*X_N where X_N is the position of the last BAC. |

`round` |
The smoothing results of either `aws`
or `laws` function are rounded or not depending on
the `round` argument. The `round` value is passed to the
argument `digits` of the `round` function. |

`verbose` |
If `TRUE` some information are printed |

`...` |
Parameters to be passed to `aws` or
`laws` function. Typical parameters are
`qlambda` , `model` , `lkern` . |

The Adaptive Weights Smoothing procedure as described by Polzehl & Spokoiny is used to fit a function piecewise constant.
Then, based on the smoothing results of either `aws`

or `laws`

function, a breakpoint is added when two contiguous smoothing values are different: breakpoints are flagged by 1 in the `Breakpoints`

vector and the flag corresponds to the last position of identical amount of DNA. A specific process is implemented for outliers detection: an outlier is a position such that the smoothing value on its right and the smoothing value on its left are equal but the smoothing value in this position is different from the right and left values. If the first position (respectively the last position) is different of the second one (respectively the next to last one) then the position is considered as an outlier.
Each outliers are flagged by 1 in the `OutliersAws`

vector.

An object of class "profileCGH" with the following added information in
the data.frame attribute `profileValues`

:

`Smoothing` |
Smoothing results of either `aws` or `laws` function after being rounded or not depending on the `round` argument. |

`Region` |
Each position between two breakpoints are labelled the same way with an integer value starting from one. The label is incremented by one when a new breakpoints occurs or when moving to the next chromosome. |

`Level` |
Each position with equal smoothing value are labelled the same way with an integer value starting from one. The label is incremented by one when a new level occurs or when moving to the next chromosome. |

`OutliersAws` |
Each outliers detected are flagged by one otherwise it is 0. |

`Breakpoints` |
The last position of a region with identical amount of DNA is flagged by 1 otherwise it is 0. |

Philippe Hupé, Philippe.Hupe@curie.fr.

data(snijders) profileCGH <- list(profileValues=gm13330) class(profileCGH) <- "profileCGH" # Estimation of the piecewise constant function res <- chrBreakpoints(profileCGH, smoothfunc="laws", lkern="exponential", model="Gaussian", qlambda=0.999, base=FALSE,bandwidth=10) plot(LogRatio ~ PosOrder, data=res$profileValues, pch=20) # Limit between chromosomes LimitChr <- unique(res$profileValues$LimitChr)+0.5 abline(v=LimitChr, col="grey", lty=2) lines(res$profileValues$Smoothing ~ res$profileValues$PosOrder, col="green") # Breakpoints identified indexBP <- which(res$profileValues$Breakpoints==1) BP <- res$profileValues$PosOrder[indexBP]+0.5 abline(v=BP, col="red", lty=2)

[Package *GLAD* version 1.0.1 Index]