pval2index {mdgsa} | R Documentation

## Transform p-values in into a ranking index.

### Description

After a genomic test, p-values are numerical indexes which account for certain biological characteristic. By definition p-values are bounded between zero and one, but this may not be suitable as an index. Moreover, p-values are always derived form a statistic which sign may be important. The function helps transforming the p-value and its associated statistic into a ranking index.

### Usage

    pval2index(pval, sign, names = NULL, log = TRUE, offset, verbose = TRUE)

### Arguments

`pval` | a vector or matrix of p-values.
`sign` | a vector or matrix of signs associated to the p-values.
`names` | a character vector of the names of the features.
`log` | = TRUE
`offset` | value used to replace p-values equal to zero
`verbose` | verbose

### Details

The default transformation is (-1) * log (pval) * sign (sign). When log = FALSE the transformation is (1 - pval) * sign (sign).

If `sign` is missing all p-values are associated wit a positive sign.

Missing values are allowed and return NA values.

An `offset` may be provided to replace p-values equal to zero when `log = TRUE`. In such way infinite values are not generated. If the `offset` parameter is not provided, the minimum p-value other than zero is used for the replacement. You can explicitly specify `offset = 0` if you want `Inf` values to be returned.

By default the names of the output vector (or row names in a matrix) are those of `pval` or `sign`. If `names` is provided, then it is used instead.

### Value

A transformed index. A vector or matrix, depending on the input parameters.

### Author(s)

David Montaner dmontaner@cipf.es

### See Also

`indexTransform`

### Examples

    my.statistic <- rnorm (1000)
    my.pvalue <- 2 * pnorm (my.statistic)
    my.pvalue[my.pvalue > 1] <- 2 - my.pvalue[my.pvalue > 1]

    index <- pval2index (pval = my.pvalue, sign = my.statistic)

    #par (mfrow = c (1,2))
    #plot (my.statistic, my.pvalue)
    #plot (my.statistic, index)

    ## Zero p-values
    p <- c (0:10)/10
    p
    pval2index (p)
    pval2index (p, offset = 0)
    pval2index (p, offset = 0.000001)

    ## Missing p-values
    p <- c(0:10, NA)/10
    p
    pval2index (p)
    pval2index (p, offset = 0)
    pval2index (p, offset = 0.000001)
    pval2index (p, log = FALSE)
    pval2index (p, offset = 0, log = FALSE)

    ## Matrix
    p <- matrix (c(0:10, NA)/10, ncol = 3)
    p
    pval2index (p)
    pval2index (p, offset = 0)
    pval2index (p, offset = 0.000001)
    pval2index (p, log = FALSE)
    pval2index (p, offset = 0, log = FALSE)

[Package mdgsa version 1.12.1 Index]