Description Usage Arguments Details Value Note References See Also Examples

View source: R/iterateBMAsurv.R

Survival analysis and variable selection on microarray data. This is a multivariate technique to select a small number of relevant variables (typically genes) to perform survival analysis on microarray data. This function performs the training, prediction, and assessment steps. The data is not assumed to be pre-sorted by rank before this function is called.

1 | ```
iterateBMAsurv.train.predict.assess (train.dat, test.dat, surv.time.train, surv.time.test, cens.vec.train, cens.vec.test, p=100, nbest=10, maxNvar=25, maxIter=200000, thresProbne0=1, cutPoint=50, verbose = FALSE, suff.string="")
``` |

`train.dat` |
Data matrix for the training set where columns are variables
and rows are observations. In the case of gene expression data,
the columns (variables) represent genes, while the rows
(observations) represent samples. If Cox Proportional Hazards
Regression is the desired univariate ranking measure, the data
does not need to be pre-sorted. To use a different univariate
ranking measure, see |

`test.dat` |
Data matrix for the test set where columns are variables and rows are observations. In the case of gene expression data, the columns (variables) represent genes, while the rows (observations) represent samples. The test set should contain the same variables as the training set. |

`surv.time.train` |
Vector of survival times for the patient samples in the training set. Survival times are assumed to be presented in uniform format (e.g., months or days), and the length of this vector should be equal to the number of rows in train.dat. |

`surv.time.test` |
Vector of survival times for the patient samples in the test set. Survival times are assumed to be presented in uniform format (e.g., months or days), and the length of this vector should be equal to the number of rows in test.dat. |

`cens.vec.train` |
Vector of censor data for the patient samples in the training set. In general, 0 = censored and 1 = uncensored. The length of this vector should equal the number of rows in train.dat and the number of elements in surv.time.train. |

`cens.vec.test` |
Vector of censor data for the patient samples in the test set. In general, 0 = censored and 1 = uncensored. The length of this vector should equal the number of rows in train.dat and the number of elements in surv.time.test. |

`p` |
A number indicating the maximum number of top univariate genes
used in the iterative |

`nbest` |
A number specifying the number of models of each size
returned to |

`maxNvar` |
A number indicating the maximum number of variables used in
each iteration of |

`maxIter` |
A number indicating the maximum iterations of |

`thresProbne0` |
A number specifying the threshold for the posterior
probability that each variable (gene) is non-zero (in
percent). Variables (genes) with such posterior
probability less than this threshold are dropped in
the iterative application of |

`cutPoint` |
Threshold percent for separating high- from low-risk groups. The default is 50. |

`verbose` |
A boolean variable indicating whether or not to print interim information to the console. The default is FALSE. |

`suff.string` |
A string for writing to file. |

This function consists of the training phase, the prediction phase,
and the assessment phase. The training phase first orders all the
variables (genes) by a univariate measure called Cox Proportional
Hazards Regression, and then iteratively applies the `bic.surv`

algorithm from the `BMA`

package. The prediction phase uses the
variables (genes) selected in the training phase to predict the risk
scores of the patient samples in the test set. In the assessment phase,
the risk scores are used to designate each test sample as either
high-risk or low-risk based on the user-designated `cutPoint`

.
Prediction accuracy is measured by the p-value difference between
groups as calculated through the central chi-square distribution. In
addition, a Kaplan-Meier Survival Analysis Curve illustrating the
difference between risk groups is written to file in the working R
directory. If Cox Proportional Hazards Regression is the desired
univariate ranking algorithm, then calling this function with the
training and testing sets is all that is necessary for a complete
survival analysis run.

If all samples are assigned to a single risk group or all samples are in
the same censor category, an error message is printed and a boolean variable
`success`

is returned as FALSE.If both risk groups are present in the
patient test samples, a Kaplan-Meier Survival Analysis Curve is written to file,
and a list with 6 components is returned:

`nvar` |
The number of variables selected by the last iteration of |

`nmodel` |
The number of models selected by the last iteration of |

`ypred` |
The predicted risk scores on the test samples. |

`result.table` |
A 2 x 2 table indicating the number of test samples in each category (high-risk/censored, high-risk/uncensored, low-risk/censored, low-risk/uncensored). |

`statistics` |
An object of class |

`success` |
A boolean variable returned as TRUE if both risk groups are present in the patient test samples. |

The `BMA`

package is required.

Annest, A., Yeung, K.Y., Bumgarner, R.E., and Raftery, A.E. (2008). Iterative Bayesian Model Averaging for Survival Analysis. Manuscript in Progress.

Raftery, A.E. (1995). Bayesian model selection in social research (with Discussion). Sociological Methodology 1995 (Peter V. Marsden, ed.), pp. 111-196, Cambridge, Mass.: Blackwells.

Volinsky, C., Madigan, D., Raftery, A., and Kronmal, R. (1997) Bayesian Model Averaging in Proprtional Hazard Models: Assessing the Risk of a Stroke. Applied Statistics 46: 433-448.

Yeung, K.Y., Bumgarner, R.E. and Raftery, A.E. (2005) Bayesian Model Averaging: Development of an improved multi-class, gene selection and classification tool for microarray data. Bioinformatics 21: 2394-2402.

`iterateBMAsurv.train.wrapper`

,
`iterateBMAsurv.train`

,
`singleGeneCoxph`

,
`predictBicSurv`

,
`predictiveAssessCategory`

,
`trainData`

,
`trainSurv`

,
`trainCens`

,
`testData`

,
`testSurv`

,
`testCens`

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | ```
library (BMA)
library(iterativeBMAsurv)
data(trainData)
data(trainSurv)
data(trainCens)
data(testData)
data(testSurv)
data(testCens)
## Use p=10 genes and nbest=5 for fast computation
ret.bma <- iterateBMAsurv.train.predict.assess (train.dat=trainData, test.dat=testData, surv.time.train=trainSurv, surv.time.test=testSurv, cens.vec.train=trainCens, cens.vec.test=testCens, p=10, nbest=5)
## Extract the statistics from this survival analysis run
number.genes <- ret.bma$nvar
number.models <- ret.bma$nmodel
evaluate.success <- ret.bma$statistics
``` |

iterativeBMAsurv documentation built on May 2, 2018, 2:06 a.m.

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