log2TransformPositive {blima} | R Documentation

## Log2 transform of numbers >1.

### Description

Transformation function are popular in beadarray package. Here this is similar concept. This function allow user to perform log transformation before doing t-tests.

### Usage

    log2TransformPositive(x)

### Arguments

`x` | Number to transform.

### Value

This function returns logarithm of base 2 for numbers >=1 and zero for numbers <1.

### Author(s)

Vojtěch Kulvait

### Examples

    if(require("blimaTestingData") && require("illuminaHumanv4.db") && interactive())
    {
        #To perform background correction, quantile normalization and then bead level t-test on log data run. Vst is not performed in this scheme. Top 10 probes is then printed according to certain measure.
        data(blimatesting)
        #Prepare logical vectors corresponding to conditions A(groups1Mod), E(groups2Mod) and both(c).
        groups1 = "A";
        groups2 = "E";
        sampleNames = list()
        groups1Mod = list()
        groups2Mod = list()
        c = list()
        for(i in 1:length(blimatesting))
        {
            p = pData(blimatesting[[i]]@experimentData$phenoData)
            groups1Mod[[i]] = p$Group %in% groups1;
            groups2Mod[[i]] = p$Group %in% groups2;
            c[[i]] = p$Group %in% c(groups1, groups2);
            sampleNames[[i]] = p$Name
        }
        #Background correction and quantile normalization followed by testing including log2TransformPositive transformation.
        blimatesting = bacgroundCorrect(blimatesting, normalizationMod =c, channelBackgroundFilter="bgf")
        blimatesting = nonPositiveCorrect(blimatesting, normalizationMod=c, channelCorrect="GrnF",  channelBackgroundFilter="bgf", channelAndVector="bgf")
        blimatesting = quantileNormalize(blimatesting, normalizationMod=c, channelNormalize="GrnF", channelOutput="qua", channelInclude="bgf")
        beadTest <- doTTests(blimatesting, groups1Mod, groups2Mod,
                transformation=log2TransformPositive, quality="qua", channelInclude="bgf")
        symbol2address <- merge(toTable(illuminaHumanv4ARRAYADDRESS), toTable(illuminaHumanv4SYMBOLREANNOTATED))
        symbol2address <- symbol2address[,c("SymbolReannotated", "ArrayAddress") ]
        colnames(symbol2address) <- c("Symbol", "ArrayAddressID")
        beadTest = merge(beadTest, symbol2address, by.x="ProbeID", by.y="ArrayAddressID")
        beadTestID = beadTest[,c("ProbeID", "Symbol")]
        beadTestFC = abs(beadTest[,"mean1"]-beadTest[,"mean2"])
        beadTestP = beadTest[,"adjustedp"]
        beadTestMeasure = (1-beadTestP)*beadTestFC
        beadTest = cbind(beadTestID, beadTestMeasure)
        colnames(beadTest) <- c("ArrayAddressID", "Symbol", "difexBL")
        sortBL = sort(-beadTest[,"difexBL"], index.return=TRUE)$ix
        beadTop10 = beadTest[sortBL[1:10],]
        print(beadTop10)
    }else
    {
        print("To run this example, please install blimaTestingData package from bioconductor by running BiocManager::install('blimaTestingData') and illuminaHumanv4.db by running BiocManager::install('illuminaHumanv4.db').");
    }

[Package blima version 1.22.0 Index]